Can iPhone dictation understand two languages at once?

Apple's pages do not describe iPhone Dictation understanding two languages in one sentence. Dictation takes its language from the keyboard you are using. Apple says that when you use a keyboard for another language, you can use Dictation in that language as well ¹. So the practical answer is no: change languages between parts of what you say, not inside a phrase.

Apple's two-language feature is for typing

The two-language feature that Apple describes is for typing. Apple says that for some supported languages, you can type in two languages without having to switch between keyboards, and that the keyboard switches automatically between the two you use most often ².

Apple's example of a bilingual keyboard is English (U.S.) and Spanish (Latin America). The option is available for select language pairs only ³. Apple does not connect that feature to Dictation on its pages. If your two languages are not a select pair, the bilingual keyboard does not apply to you at all.

Switch with the Globe key between parts of a sentence

Hold the Globe key to see all of your enabled keyboards, or tap it to move to the next one ⁴. The key appears only when more than one keyboard is enabled ⁵, so if you cannot find it, add the second keyboard first.

For a sentence in two languages, this routine works on any iPhone with both keyboards enabled:

1. Switch to the first language with the Globe key, then dictate that part.
2. Switch to the second language, then dictate the next part.
3. Read the whole text afterwards, and fix any word that came out in the wrong language.

Android's Gboard works differently, and some Pixel phones switch on the fly

On Android, Gboard switches languages from its voice toolbar. At the bottom left of the toolbar, tap the abbreviation for your default language, then select a language ⁶.

Some newer Pixel phones go further. In October 2023, 9to5Google reported that on Pixel 8 and Pixel 8 Pro, voice typing in Gboard could recognize multiple languages and switch between them on the fly ⁷.

Those are Pixel reports from 2023. The sources checked for this answer do not show that every Android phone mixes two languages inside one sentence, so do not assume it on yours.

It depends on the phone, the language pair and the punctuation

• Phone: Apple's pages describe no mixed-language Dictation on iPhone. The on-the-fly switch is reported for the Pixel 8 and Pixel 8 Pro, and the sources checked here do not show it on other models.
• Language pair: the bilingual keyboard applies only to select pairs, as noted above.
• Punctuation: Google says punctuation phrases might not be available in every language that Gboard voice typing supports ⁸. A spoken mark may work in one language and not the other, so type any mark that does not appear.

What to do

For one sentence in two languages, switch before each part and check the text afterwards. Do not count on automatic detection on iPhone. Apple's pages describe Dictation as following the keyboard, not as detecting which language you are speaking, so plan to switch yourself.

For the full comparison of the two systems, read the guide to dictation languages on iPhone and Android. Two related questions are why your dictation language is not showing and why iPhone dictation types in the wrong language. For the whole subject, see dictation and voice to text on iPhone and Android.