Is speaking two languages causing my child’s speech delay?

If your child isn’t talking as much as you expected, or their speech is hard for other people to follow, it’s common to wonder whether the two languages at home are behind it. Plenty of families are told exactly that, sometimes by people they trust. So it’s worth saying plainly: the evidence doesn’t support it.

The short answer

Growing up with two languages does not cause a speech or language delay, and it doesn’t cause developmental language disorder. Royal College of Speech and Language Therapists guidance puts it directly: bilingualism is not a disorder, and there’s no reason bilingual children should have a different rate of speech and language problems from children learning one language. The Hanen Centre and ASHA say the same.

That doesn’t make your concern misplaced. A bilingual child can absolutely have a genuine communication difficulty. It’s simply that the two languages aren’t the cause, and dropping one won’t fix it.

Speech and language are two different things

These get muddled, and the difference matters. Speech is producing sounds clearly: whether your child says “tar” for “car”, or leaves the ends off words. Language is understanding and using words and sentences. A child might have clear speech but few words, or plenty to say but be hard to follow.

What the research shows

A 2025 longitudinal study followed 302 bilingual and 302 matched monolingual children, tracking milestones from babbling to first word, fiftieth word and first word combinations. The bilingual children reached them at comparable ages. Typical bilingual development, the authors concluded, follows a trajectory similar to monolingual development.

There’s one honest nuance. Within a single language, bilingual children often know fewer words than a monolingual of the same age, because their listening time is split. Hoff and Core call this a single-language lag, not a problem with the child, which is why the picture across both languages is fairer.

Looking at one language underestimates what your child knows

If your child says “سيارة” in Arabic and “ball” in English, those are two words they can use. Counting only one language makes their vocabulary look smaller than it is. As Byers-Heinlein and Lew-Williams put it, a bilingual toddler with fifty words in each language won’t look as capable as a monolingual cousin with ninety English words, even though they know more overall. Clinicians count this differently: total vocabulary adds up every word across both languages, while conceptual vocabulary credits a child who knows both “سيارة” and “car” once for the concept. It’s fair to ask which a therapist used.

Peña, Bedore and Granados Vargas studied 595 Spanish-English bilingual children aged five to twelve, 100 of whom had developmental language disorder. Testing in Spanish alone, or English alone, produced scores that tracked how much of each language the child happened to hear. When the best score across both languages was used instead, that link disappeared: differences then related to ability, not exposure. Bilingual children, they note, are both over-identified and under-identified with language disorder, and single-language testing is part of why.

Expect one language to be stronger. A child who hears Arabic at home and English at nursery may know more about colours in English and more about meals in Arabic. That reflects where they spend their time, not their ability. Ask nursery staff what your child understands with them, because you may be seeing only part of it.

Mixing languages is not confusion

Using both languages in one sentence, sometimes called code-mixing, is a normal feature of bilingual development, not a sign a child has muddled the two. Byers-Heinlein and Lew-Williams note that bilingual children mix for good reasons, often reaching for the word they have when the other hasn’t arrived, and that even toddlers adjust their choice depending on who they’re talking to. Correcting every instance makes conversation harder work for no benefit.

A note for Arabic-speaking families

Arabic adds a layer that English-language advice tends to skip. Your child may hear one spoken dialect at home, meet Modern Standard Arabic in books and school, and use English elsewhere. Saiegh-Haddad and Ghawi-Dakwar found Arabic-speaking children repeated items less accurately when those items contained Standard Arabic sounds absent from their dialect, and the effect was larger in children with language impairment. So an unfamiliar form on a test isn’t automatically evidence of difficulty, and a therapist needs to know which dialect your child hears. Research here is still limited compared with English, so a good clinician will say so and lean on your account of what’s usual at home.

What you can try at home

Keep speaking the language that feels most natural to you, during play, mealtimes, bath time and shared books. Hoff and Core are explicit that parents shouldn’t be discouraged from speaking their first language to their children, and Hanen advises using whichever you’re most comfortable with. Warm conversation in your strongest language does more than stilted conversation in one you don’t hold as easily.

A few things that tend to help:

• Follow what your child is interested in and comment on it, rather than asking them to name things. Hanen suggests letting your child start the interaction, responding straight away, then leaving space, up to ten seconds, for their next turn.
• Repeat what they say and add a little. If they say “car”, you might say “Yes, the car is going!”
• Accept an answer in either language rather than asking them to repeat it in the other one.
• Keep a short running list of the words they use in each language. It builds a fuller picture, and it’s useful for a therapist.
• Skip the testing. Asking a child to perform words on demand usually produces less talking, not more.

None of these will suit every child. If something doesn’t fit yours, leave it.

When it’s worth speaking to a speech and language therapist

These aren’t cut-offs to score yourself against. They’re reasons to ask someone.

• Your child is losing words or skills they previously had.
• There’s little or no progress over several months in either language.
• They find familiar words or simple instructions hard to understand across their languages.
• They use very few gestures, sounds or attempts to communicate.
• Their speech is much harder to understand than you’d expect at their age, in both languages.
• Communication difficulties are causing real frustration, or affecting how they join in at home, nursery or school.
• You, or their teachers, are still concerned even after being told it’s “just bilingualism”.
• You have any concern about their hearing, in which case a hearing check should come first or alongside.

You don’t need to wait for a milestone to pass. If you’re worried, that’s reason enough.

What a good assessment looks like

Ask that it considers your child’s full language background and their abilities across all their languages. RCSLT guidance calls assessing every language a child speaks essential, and ASHA guidance recommends gathering samples in all of them, with an interpreter where necessary, while recognising that patterns caused by one language influencing the other are not signs of a disorder.

The therapist doesn’t have to speak Arabic. McLeod, Verdon and the International Expert Panel on Multilingual Children’s Speech describe how a clinician who doesn’t share a child’s languages can still assess well: working with trained interpreters or bilingual colleagues, taking a full language history, using informal tasks where standardised tests don’t exist, and involving parents directly, including comparing the child’s speech with a parent’s own.

If you’ve been advised to stop speaking your home language, you’re entitled to ask for a proper assessment instead.

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Sources

• Peña, E. D., Bedore, L. M., & Granados Vargas, A. (2023). Exploring assumptions of the bilingual delay in children with and without developmental language disorder. Journal of Speech, Language, and Hearing Research, 66(12), 4739–4755. https://doi.org/10.1044/2023_JSLHR-23-00117
• Muszyńska, K., Krajewski, G., Dynak, A., Garmann, N. G., Romøren, A. S. H., Łuniewska, M., Alcock, K., Katsos, N., Kołak, J., Simonsen, H. G., Hansen, P., Krysztofiak, M., Sobota, K., & Haman, E. (2025). Bilingual children reach early language milestones at the same age as monolingual peers. Journal of Child Language, 53(2), 365–388. https://doi.org/10.1017/S0305000924000655
• Hoff, E., & Core, C. (2015). What clinicians need to know about bilingual development. Seminars in Speech and Language, 36(2), 89–99. https://doi.org/10.1055/s-0035-1549104
• Byers-Heinlein, K., & Lew-Williams, C. (2013). Bilingualism in the early years: What the science says. LEARNing Landscapes, 7(1), 95–112. https://www.learninglandscapes.ca/index.php/learnland/article/view/Bilingualism-in-the-Early-Years-What-the-Science-Says
• Saiegh-Haddad, E., & Ghawi-Dakwar, O. (2017). Impact of diglossia on word and non-word repetition among language impaired and typically developing Arabic native speaking children. Frontiers in Psychology, 8, 2010. https://doi.org/10.3389/fpsyg.2017.02010
• McLeod, S., Verdon, S., & the International Expert Panel on Multilingual Children’s Speech (2017). Tutorial: Speech assessment for multilingual children who do not speak the same language(s) as the speech-language pathologist. American Journal of Speech-Language Pathology, 26(3), 691–708. https://doi.org/10.1044/2017_AJSLP-15-0161
• Stow, C., & Pert, S. SLT assessment and intervention: Best practice for children and young people in bilingual settings. Royal College of Speech and Language Therapists. https://www.rcslt.org/wp-content/uploads/media/Project/RCSLT/best-practice-cyp-bilingual-settings.pdf
• American Speech-Language-Hearing Association. Multilingual service delivery in audiology and speech-language pathology (Practice Portal). https://www.asha.org/practice-portal/professional-issues/multilingual-service-delivery/
• American Speech-Language-Hearing Association. Learning more than one language. https://www.asha.org/public/speech/development/learning-more-than-one-language/
• The Hanen Centre. Speaking more than one language with my child. https://www.hanen.org/information-tips/speaking-more-than-one-language-with-my-child

Further reading

• Paradis, J., Genesee, F., & Crago, M. B. (2021). Dual language development and disorders: A handbook on bilingualism and second language learning (3rd ed.). Baltimore, MD: Brookes Publishing.