The study investigates the effects of grammatical gender on bilingual processing. Native speakers of Russian (a gendered language) learning English and monolingual English controls performed a self-paced reading task in English (a non-gendered language). As predicted, bilingual speakers showed delayed latencies to gendered pronouns (he or she) that were incongruent with the noun's grammatical gender in Russian, indicating that first language (L1) grammatical gender assignment can be interpreted as biological gender in nonnative (L2) processing. The L1 gender bias was only found in sentences containing animate, but not inanimate, nouns. These results speak against the syntactic mechanism being solely responsible for gender biases, but rather support a semantic transfer account due to coactivation of linguistic and conceptual features as proposed in the sex and gender hypothesis (SAGH, Vigliocco, Vinson, Paganelli & Dworzynski, 2005). Overall, the study provides clear evidence for the L1 grammatical gender bias in bilingual processing, albeit constrained by animacy.