The current study investigated the comprehension of subject and object relative clauses (RCs) in bilingual Mandarin-English children (N = 55, Mage = 7;5, SD = 1;8) and language-matched monolingual Mandarin-speaking children (N = 59, Mage = 5;4, SD = 0;7). The children completed a referent selection task that tested their comprehension of subject and object RCs, and standardised assessments of vocabulary knowledge. Results showed a very similar pattern of responding in both groups. In comparison to past studies of Cantonese, the bilingual and monolingual children both showed a significant subject-over-object RC advantage. An error analysis suggested that the children’s difficulty with object RCs reflected the tendency to interpret the sentential subject as the head noun. A subsequent corpus analysis suggested that children’s difficulty with object RCs may be in part due to distributional information favouring subject RC analyses. Individual differences analyses suggested cross-linguistic transfer from English to Mandarin in the bilingual children at the individual but not the group level, with the results indicating that comparative English-dominance makes children vulnerable to error