Mutual Exclusivity Constraints (ME) are one of the cognitive constraints proposed to account for the speedy growth of vocabulary in children. It refers to the tendency to assume that one object should have only one label. It is also found that monolingual children are more inclined to apply such an assumption that their bilingual counterparts. In this study, we examined the performance of 4 to 6-year-old Chinese monolingual and bilingual children in this regard. According to their educational backgrounds and scores on language tests, these children were divided into three language groups: Mandarin monolingual, Mandarin-Taiwanese bilingual and Mandarin-English bilingual. Two experimental tasks were used to examine (1) their ability to match familiar and unfamiliar objects with nonce-words and (2) their receptiveness to the naming of novel blended objects with labels that come from constituent parts. Our findings indicate that monolingual children and bilingual children differ from each other in their use of ME. Children in the monolingual group applied ME to infer the referent of a nonce-word more often than children in the bilingual groups did. The two bilingual groups also displayed differences in receptivity to new words: the Mandarin-Taiwanese group suspended the use of ME while the Mandarin-English group expected new names for novel objects. In addition, we also found that adjustments in the use of ME observed in our bilingual subjects can be divided into two types according to the scope of application namely, global adjustment and local adjustment. The former needs to be triggered by a higher level of second language proficiency but the latter does not.