Bilingual babies start talking at roughly the same age as monolingual babies, typically producing their first words around 12 months. Despite a persistent worry that learning two languages causes speech delays, the research consistently shows that bilingual children hit early language milestones on a similar timeline. What can differ is how their vocabulary is distributed across two languages, which sometimes creates the impression of a delay when there isn’t one.
Early Milestones Follow the Same Timeline
Whether a baby is hearing one language or two, the progression of sound development is remarkably consistent. Babies coo and make pleasure sounds from birth to about 3 months. Between 4 and 6 months, they begin babbling in speech-like ways, experimenting with sounds that start with p, b, and m. From 7 months to a year, babbling gets more complex, with longer strings of syllable-like sounds (“tata,” “upup,” “bibibi”). Most babies produce one or two recognizable words like “mama,” “dada,” or “hi” by their first birthday.
Bilingual babies follow this same sequence. They may babble using sounds from both of their languages, and their first words might come from either language or a mix of both. A bilingual baby’s first word is just as likely to appear at 11 months as a monolingual baby’s.
Why Bilingual Toddlers Can Seem Behind
The confusion usually starts when parents or pediatricians count words in only one language. A 22-month-old bilingual toddler might know 80 words in Spanish and 90 words in English. If you only test the English, the child looks like they know fewer words than a monolingual English-speaking peer. But their total vocabulary across both languages is 170 words, which is right on track or even ahead.
Researchers distinguish between “total vocabulary” (every word a child knows in both languages combined, including duplicates like “dog” and “perro”) and “conceptual vocabulary” (counting translation equivalents only once). A study of Spanish-English bilingual children found that at 22 months, their average conceptual vocabulary was about 178 words, growing to roughly 299 words by 25 months. When researchers used total vocabulary as the measure, bilingual children were not significantly different from monolingual peers at any time point tested. The gap only appeared when using conceptual vocabulary, which by definition undercounts what a bilingual child actually knows.
This is a measurement problem, not a language problem. A bilingual toddler who says “water” at home and “agua” at grandma’s house has two words for one concept. Counting that as just one word undersells what the child can do.
Understanding Comes Before Speaking
Bilingual children often understand far more than they say, and this gap between comprehension and speech can be wider than in monolingual children. Receptive language (what a child understands) typically develops faster and stays more balanced across both languages than expressive language (what a child actually says). Research tracking bilingual children over several years found that even after years of majority-language schooling, over half maintained balanced comprehension in both languages, while their spoken output shifted heavily toward the dominant language.
This means your toddler may understand instructions perfectly in both languages but respond mostly in one. That’s normal bilingual development, not a sign of confusion or delay. A 20-month-old who follows directions in Mandarin but only speaks English words is demonstrating strong receptive skills in both languages.
Language Mixing Is a Skill, Not Confusion
One of the biggest concerns parents have is when their toddler mixes languages in a single sentence. This is called code-switching, and it’s a normal, well-documented part of bilingual development that begins early in language acquisition.
Children code-switch for practical reasons. When they don’t yet know a word in the language they’re speaking, they borrow it from their other language to fill the gap. A toddler who says “I want leche” isn’t confused about which language is which. They’re using the word they have available to communicate effectively. Research shows that children as young as 2 are already sensitive to which language each person around them speaks, and they adjust their code-switching accordingly.
Bilingual toddlers tend to code-switch more into the majority language (the one spoken more widely in their community) than the reverse. In Spanish-English bilingual toddlers in the U.S., for instance, children were more likely to insert English words into Spanish sentences than the other way around. This pattern reflects the child’s language environment more than any deficit in ability.
Red Flags That Apply to All Children
Bilingualism does not cause speech or language disorders. The red flags for concern are the same regardless of how many languages a child hears:
- By 9 months: no babbling at all
- By 12 months: no pointing or gesturing
- By 15 months: not following another person’s gaze or attention
- By 16 months: no single intelligible words in either language
- By 24 months: no two-word phrases in either language, or inability to follow simple directions like “come here” or “sit down”
- By 36 months: speech mostly unintelligible to familiar listeners
- At any age: loss of language skills the child previously had, or inconsistent response to sounds
The key distinction: these benchmarks apply across both languages combined. A child who isn’t producing single words in either language by 16 months warrants evaluation. A child who says 10 words in Portuguese and 3 in English at 16 months is fine. If there are significant concerns, a speech-language evaluation should ideally assess both languages, since testing in only one can make a typically developing bilingual child look delayed.
What Actually Helps Bilingual Babies Talk
The most important factor in bilingual language development isn’t which strategy you pick. It’s the quantity and quality of input in each language. Children need rich, interactive exposure to build vocabulary, and that’s true whether you’re speaking one language or two.
The “one parent, one language” approach, where each parent consistently speaks a different language, is probably the most well-known strategy. Research shows it can work well, but it’s neither necessary nor guaranteed to succeed on its own. Children who hear both languages from the same bilingual parent also frequently learn both languages successfully. Other families alternate by location (one language at home, another outside) or by time of day. No single method has proven superior.
What does matter is ensuring enough exposure to the minority language, the one your child won’t hear as much in the broader community. Many experts recommend providing slightly more early input in the minority language and, when possible, creating opportunities for children to interact with other kids in that language. Playgroups, family visits, and community events in the minority language can make a meaningful difference, because children learn language best through social interaction rather than passive listening.
Reading aloud, narrating daily activities, and singing songs in both languages all build the kind of rich input that supports vocabulary growth. The goal isn’t to follow a rigid system but to make sure both languages show up consistently and naturally in your child’s life.