Two studies explored young children’s understanding of the role of shared language in communication by investigating how monolingual English-speaking children interact with an English speaker, a Spanish speaker, and a bilingual experimenter who spoke both English and Spanish. When the bilingual experimenter spoke in Spanish or English to request objects, four-year-old children, but not three-year-olds, used her language choice to determine whom she addressed (e.g. requests in Spanish were directed to the Spanish speaker). Importantly, children used this cue – language choice – only in a communicative context. The findings suggest that by four years, monolingual children recognize that speaking the same language enables successful communication, even when that language is unfamiliar to them. Three-year-old children’s failure to make this distinction suggests that this capacity likely undergoes significant development in early childhood, although other capacities might also be at play.