This research examines whether an individual's linguistic knowledge, either as a speaker of a particular language or as a bilingual, influences theory of mind development. Three- and four-year-old English monolinguals, Mandarin Chinese monolinguals, and Mandarin-English bilinguals were given appearance-reality, level 2 perspective-taking, and false-belief tasks. All children were tested twice, a week apart; the bilinguals were tested in each of their languages. The 4-year-olds in each group performed significantly better than the corresponding 3-year-olds. Both monolingual groups performed similarly on the tasks, and the bilinguals performed significantly better than the monolingual groups, although when the two testing times were examined separately, they had only a near-significant tendency to perform better at the second testing time. Possible explanations for this evidence of a bilingual advantage are greater inhibitory control, greater metalinguistic understanding, and a greater sensitivity to sociolinguistic interactions with interlocutors.