Bilingual Child Development: What's Normal and What's Not
By Natalie Zorilla, Bilingual Speech Language Pathologist, CCC SLP | Pediatric Developmental & Behavioral Health Navigation
You are raising your child in two languages. Maybe you and your partner speak different languages at home. Maybe you are an immigrant family holding tightly to your native language while your child absorbs English from daycare, school, and the world around them. Maybe you made a deliberate choice to raise a bilingual child because you believe rightly that it is a gift.
And then someone said something that planted a seed of worry.
Maybe it was your pediatrician suggesting your child's speech delay might be because of the two languages. Maybe it was a well-meaning relative telling you to just speak English so your child does not get confused. Maybe it was a preschool teacher who seemed concerned. Maybe it was just you, at 2am, wondering if you are doing something wrong.
You are not doing something wrong. But you do deserve clear, honest, research-backed information because there is a tremendous amount of myth, misinformation, and outdated thinking floating around on this topic, including sometimes in medical offices.
This article is here to give you that clarity. What bilingual development actually looks like, what is completely normal, what genuine warning signs look like, and how to advocate for your child if someone tries to tell you the problem is the language.
Learn more -> Does speaking another language at home cause confusion
First: The Research Is Clear on This
Bilingualism does not cause language delays. This is not a matter of ongoing scientific debate. Decades of research in linguistics, developmental psychology, and speech-language pathology have established this conclusively.
Children are neurologically wired to acquire multiple languages simultaneously. The human brain and especially the young child's brain is extraordinarily well-equipped for this. Children around the world grow up bilingual and multilingual as the norm, not the exception. The majority of the world's population speaks more than one language.
What bilingualism does do is make the path to language acquisition look different. Not delayed. Different. And understanding that difference is everything.
How Bilingual Language Development Actually Works
To understand what is normal, you first need to understand how bilingual children acquire language because it does not look exactly like monolingual acquisition, and that difference gets misread as a problem constantly.
Simultaneous vs. sequential bilingualism
Simultaneous bilingualism is when a child is exposed to two languages from birth or very early infancy typically before age 3. These children acquire both languages at the same time and develop two first languages simultaneously.
Sequential bilingualism is when a child acquires one language first and then begins learning a second language later typically after age 3. This is common in children who grow up speaking one language at home and then enter an English-speaking school or childcare environment.
Both are normal. Both produce fully bilingual individuals. But the developmental path looks different for each, and both look different from monolingual development.
The one system, two languages reality
Young bilingual children do not have two completely separate language systems operating in parallel. Early in development, they have one integrated language system that contains words, sounds, and structures from both languages. Over time typically by age 3 or 4 the two languages become increasingly differentiated.
This integration is normal and healthy. It is not confusion. It is the brain doing exactly what it is supposed to do.
Total vocabulary is what matters
This is one of the most important things to understand: when assessing a bilingual child's vocabulary, you must count words across both languages together, not just in one language.
A bilingual child might know "dog" in English and "perro" in Spanish but not both. They might know "agua" but not "water." If you only count English words, their vocabulary looks smaller than it is. Their total conceptual vocabulary words they know in any language is what should be compared to developmental norms.
Bilingual children typically have smaller vocabularies in each individual language than monolingual peers, but their combined vocabulary across both languages is comparable to and often exceeds what monolingual children know.
What Is Completely Normal in Bilingual Children
Here is a list of things that are normal, healthy, and not signs of a language disorder even though they sometimes get flagged as concerning.
Code-switching
Code-switching is when a bilingual speaker moves between languages within a single conversation or even within a single sentence "Can I have some agua?" or "Let's go to the parque."
This is not confusion. This is not a sign that the child cannot keep the languages straight. Code-switching is a sophisticated linguistic behavior that even fully proficient adult bilinguals do. It follows grammatical rules. It is purposeful. Research shows that bilingual children code-switch in systematic, rule-governed ways from a very young age.
When your child mixes languages, they are not failing at either language. They are doing something cognitively complex and linguistically sophisticated.
A silent period
When a child who speaks one language is suddenly immersed in a second language entering an English-speaking preschool when they speak Spanish at home, for example they often go through a silent period. They stop talking as much, or stop talking in one language almost entirely, while they absorb and process the new language.
This silent period is normal and expected. It typically lasts a few weeks to a few months. It can alarm parents and teachers who are watching a previously talkative child go quiet. But it is a sign of normal language processing, not regression or disorder.
Uneven language development across the two languages
Bilingual children almost never develop both languages at exactly the same pace or to exactly the same level. The language they hear more, use more, and need more will be stronger. This is called language dominance, and it is completely normal and it can shift over time as the child's environment changes.
A child who speaks mostly Spanish at home may enter school with strong Spanish and emerging English. A few years later their English may surpass their Spanish as school becomes their dominant environment. This is expected and does not indicate a problem with either language.
Smaller single-language vocabulary
As discussed above, it is completely normal for a bilingual child to have a smaller vocabulary in each individual language compared to monolingual peers. The key is that their total vocabulary across both languages should still fall within normal developmental ranges.
If a child is assessed only in English as often happens in school or clinical settings — their results will look weaker than they actually are. This is a significant source of misdiagnosis and inappropriate referrals, and it is something you need to advocate against.
Later language dominance shifts
It is normal for a bilingual child's dominant language to shift sometimes dramatically as their environment changes. Children who move between countries, change schools, or enter new language environments may appear to lose ground in one language while gaining in another. This is a normal response to changing linguistic input, not a disorder.
What the Milestones Actually Look Like for Bilingual Children
Here is the critical nuance: the developmental milestones for communication still apply to bilingual children but they must be interpreted correctly.
By 12 months, bilingual children should be babbling, using a few words (in either language), making eye contact, pointing, and responding to their name just like monolingual children.
By 18 months, bilingual children should have at least 10 words total across both languages, be using words more than gestures to communicate, and showing clear communicative intent.
By 24 months, bilingual children should have at least 50 words total across both languages and be beginning to combine words into two-word phrases in at least one language.
By 36 months, bilingual children should be producing sentences of three or more words in at least one language, be generally understandable to familiar adults, and be demonstrating clear comprehension in both language environments.
The milestones are essentially the same, what changes is how you count. Total words across both languages. Development in at least one language, not necessarily both equally.
What Is NOT Normal Real Warning Signs to Watch For
Now for the part that is just as important: what genuinely warrants concern. Because bilingualism does not protect against language disorders, developmental delays, or autism. A bilingual child can absolutely have a language delay that has nothing to do with being bilingual.
The key is distinguishing between what is a normal feature of bilingual development and what is a genuine developmental concern that would be present regardless of language exposure.
Not meeting milestones in either language
If a child is not meeting communication milestones in either language, not just one that is a red flag. A bilingual child with a true language disorder will show delays across both languages, not just the weaker one. If your child has very limited vocabulary in both Spanish and English at age 2, that warrants evaluation regardless of the bilingual context.
No words in any language by 15–18 months
Bilingualism does not explain having no words at all by 15 to 18 months. All children bilingual or not should have some words by this point. If your child has no words in any language by 15 to 18 months, pursue an evaluation.
Not combining words in any language by 30 months
Bilingual children may combine words in one language before the other, but they should be combining words in at least one language by 24 to 30 months. No word combinations in either language by 30 months warrants evaluation.
Loss of previously acquired words in both languages
Language regression losing words your child previously had is always a red flag, regardless of bilingual status. If your child used to say words in Spanish and English and has stopped, that warrants prompt evaluation.
Difficulty understanding in both language environments
There is a difference between not knowing a word in English (normal for a bilingual child) and not understanding what is being communicated in either language. If your child seems not to understand directions, questions, or communication in both their home language and their school language, that is a concern.
Social communication differences present in both languages
If your child avoids eye contact, does not engage in back-and-forth interaction, does not point to share interest, or shows limited social awareness, these patterns are consistent regardless of which language the interaction is happening in that warrants evaluation for autism or other developmental concerns. These patterns are not caused by bilingualism.
Frustration and communication breakdown in both languages
A bilingual child may be frustrated when they cannot find a word in one language, but they can usually find it in the other. If your child is significantly frustrated and unable to communicate effectively in either language, that goes beyond the expected challenges of bilingual development.
The Myth That Will Not Die: "Just Speak One Language"
You have probably heard it. From a pediatrician. From a teacher. From a relative. Maybe from multiple sources.
"If your child is delayed, you should just speak one language at home. It will be less confusing."
This advice is not supported by research. It never has been. And it causes real harm because it asks families to give up their native language, their cultural identity, and their deepest form of connection with their child, based on a misconception.
Here is what the research actually shows:
Switching to one language does not speed up language development in children with true language disorders. A child with a language disorder will have a language disorder in one language just as they would in two.
Giving up the home language has real costs. Language is how families connect, how culture is transmitted, how grandparents talk to grandchildren. The emotional and cultural costs of abandoning the home language are significant and lasting.
Bilingualism has cognitive benefits. Research consistently shows that bilingual individuals demonstrate advantages in executive function, cognitive flexibility, and attention. Being bilingual is an asset.
If a provider tells you to stop speaking your home language, it is appropriate to ask them to cite the research behind that recommendation. You will not find it because it does not exist.
How to Advocate for Your Bilingual Child in Clinical and School Settings
The single biggest risk for bilingual children is being misdiagnosed either over-identified (flagged as having a language disorder when they are just developing bilingually) or under-identified (having a real language disorder dismissed as "just the bilingualism").
Here is how to advocate:
Insist on assessment in both languages. Any speech or language evaluation of a bilingual child should include assessment in both languages. An evaluation conducted only in English will underestimate your child's abilities. Ask specifically whether the evaluator has experience assessing bilingual children and whether they will assess in both languages.
Provide information about language exposure. Before any evaluation, give the evaluator a detailed picture of your child's language environment which language is spoken by whom, how much exposure to each language per day, when the second language was introduced, and which language your child seems stronger in. This context is essential for accurate interpretation of results.
Ask about bilingual norms. Standardized tests are typically normed on monolingual populations. Ask whether the evaluator is using bilingual norms or adjusting their interpretation to account for bilingual development.
Push back on the "drop one language" advice. Politely but firmly. Ask for the research. Ask for an alternative explanation. Seek a second opinion from a speech-language pathologist who specializes in bilingual language development if you feel your concerns are not being taken seriously.
Document both languages. Keep notes on what words your child uses in each language. Videos are extremely helpful. If you go into an evaluation with a list of words your child uses in both Spanish and English, you are giving the evaluator something real to work with.
When to Seek an Evaluation
Seek a speech-language evaluation if:
Your child is not meeting milestones in either language by the ages described above.
Your child had words in any language and lost them.
Your child seems unable to understand communication in either language environment.
Your child is significantly frustrated and unable to communicate effectively in either language.
You notice social communication differences, limited eye contact, reduced interest in interaction, no pointing to share interest across both language contexts.
Your gut is telling you something is not right, regardless of what anyone else says.
Finding an SLP who specializes in bilingual language development is ideal. These clinicians have specific training in differentiating typical bilingual development from true language disorders, and they are equipped to assess and treat in both languages. They exist they may just take a little more effort to find.
What Bilingual Speech Therapy Looks Like
If your child does receive a diagnosis of a language disorder, the good news is that bilingual children can and should receive support in both languages. Research shows that intervention in the home language transfers to the second language building skills in Spanish, for example, strengthens the underlying language system that supports English development as well.
Bilingual speech therapy may look like:
Sessions conducted in the home language, the school language, or both depending on the goals and the child's needs.
Parent coaching that helps you support your child's language development in your native language at home.
Goals that are meaningful across both language environments, not just the language of school.
If an SLP tells you they can only work in English or suggests you stop speaking your home language to your child, seek a second opinion.
How Aldea Can Help
Finding a speech-language pathologist who is experienced with bilingual children and who speaks your family's language is harder than it should be. Most generic provider directories give you no way to filter for this. You end up calling practice after practice, explaining your situation from scratch each time, often to find out they do not have bilingual clinicians or experience with bilingual assessment.
Aldea connects families to pediatric speech and developmental health providers, and we understand that for bilingual families, finding the right fit means finding someone who understands your child's full linguistic world not just one half of it.
Find a bilingual-informed provider through Aldea today.
Frequently Asked Questions
Will speaking two languages at home confuse my child? No. Children are neurologically designed to acquire multiple languages. What looks like confusion like mixing languages in a sentence is actually a sophisticated linguistic behavior that follows its own rules. It is not a sign of confusion or disorder.
Should I speak to my child in English even if it is not my strongest language? No. Research strongly supports speaking to your child in the language you are most fluent and comfortable in. The richness of your language your vocabulary, your grammar, your emotional expressiveness matters more than which language you use. A child benefits far more from rich, connected conversation in your native language than from stilted, limited English.
Can a bilingual child have a language disorder? Absolutely. Bilingualism does not protect against language disorders, autism, or other developmental conditions. The key is accurate assessment that accounts for bilingual development so that true disorders are identified and typical bilingual variation is not pathologized.
My child speaks one language at home and started school in English. Now they seem to be losing their home language. Is this normal? Unfortunately, yes this is called subtractive bilingualism, and it is extremely common when children enter an English-dominant school environment without enough continued support for the home language. Continuing to speak the home language at home, reading books in the home language, and maintaining connection to the home language community are all important for preventing significant home language loss.
At what age is it too late to introduce a second language? It is never too late to learn a second language, though the process looks different at different ages. The early childhood years particularly birth to age 7 are the most efficient time for acquiring a second language with native-like fluency. But adolescents and adults can and do become highly proficient bilinguals as well.
How do I find a speech-language pathologist who works with bilingual children? Look for SLPs who list bilingual assessment or bilingual speech therapy as a specialty. Ask specifically whether they can assess in your child's home language and whether they have experience differentiating typical bilingual development from language disorders. Aldea can help you find providers with this specific expertise.
Aldea is a care navigation platform connecting families to pediatric developmental and behavioral health providers. This article is for informational purposes only and does not constitute medical advice. Please consult a qualified healthcare provider with any questions about your child's development.