Basque speakers use dative case and agreement with animate, specific direct objects, a pattern that has been argued to be an instance of contact-induced Differential Object Marking (DOM) stemming from contact with the leísta dialect of Spanish spoken in the Basque Autonomous Community. This study compares the oral production of DOM in Basque and in Spanish by bilingual and monolingual children and by adults. While the bilingual children produced few tokens of DOM in Spanish, both bilingual and monolingual children used DOM in Basque more frequently than adults. In addition, bilingual children produced DOM at the same age in both Basque and Spanish, but at an earlier age in Basque than monolingual children do, suggesting that bilingualism in Spanish may accelerate the use of DOM in Basque. The implications of these findings for grammatical innovations driven by language contact are discussed.