The paper uses micro-data from the Spanish National Immigrant Survey to examine an uncharted question: are multilingual immigrants superior at learning the destination language? The article adopts an instrumental variable (IV) approach where the number of foreign languages known by the immigrant is instrumented using the following variables: 1. the number of nationalities of the immigrant's father and 2. the number of foreign countries where the individual has settled prior to his arrival in Spain. Above all, these instruments pass well several validity tests. The IV estimates show that for every additional foreign language learned by the immigrant the probability of being proficient in the destination language – Spanish – increases by 10.7 percent. This effect is equivalent to multiple years of formal education, to living in Spain for more than 4 years, and as important as having a mother tongue linguistically close to Spanish. We find mild evidence that women reap larger benefits from multilingualism than men (13.0 against 10.0 percent).