This study reports a production experiment investigating the realization of objects with different verb types in controlled discourse contexts in 68 three- to seven-year-old sequential Cantonese–English bilingual children. The results show the bilingual children behaved similarly to the Cantonese monolingual peers in object omission, but exhibited protracted development and produced target-deviant forms following a Cantonese pattern in omitting objects specified in prior discourse in English. The bilingual children also showed non-target-like uses of the Cantonese post-verbal object pronoun keoi5, which were unattested in monolingual children. Our findings show evidence for bidirectional cross-linguistic influence: the direction of influence goes from the weaker to the stronger language and from the stronger to the weaker language. Vulnerability of object realization in bilingual acquisition can be better understood in terms of the interaction between cross-linguistic influence, input (e.g., quantity and structural frequencies) and other linguistic elements involved in the interface relation (e.g., verb type).