The focus of this study is the acquisition of grammatical gender in Greek and Dutch by bilingual children whose other language is English. Although grammatical gender languages share the property of noun classification in terms of grammatical gender, there are important differences between the languages under investigation here in terms of both the morphological cues for gender marking available to the child and the developmental path followed by monolingual children. Dutch offers limited input cues for grammatical gender, but Greek shows consistent and regular patterns of morphological gender marking on all members of the nominal paradigm. This difference is associated with the precocious pattern of gender acquisition in Greek and the attested delay in monolingual Dutch development. We explore the development of gender in Dutch and Greek with the aim of disentangling input from age of onset effects in bilingual children who vary in the age of first exposure to Dutch or Greek. Our findings suggest that although bilingual Greek children encounter fewer difficulties in gender acquisition compared to bilingual Dutch children, amount of input constitutes a predictive factor for the pattern attested in both cases. Age of onset effects could be partly responsible for differences between simultaneous and successive bilinguals in Greek, but this is clearly not the case for Dutch. Our findings are also addressed from the more general perspective of the status of “early” and “late” phenomena in monolingual acquisition and the advantages of investigating these from the bilingual perspective.