Neighborhood density--the number of words that sound similar to a given word (Luce & Pisoni, 1998)--influences word learning in native English-speaking children and adults (Storkel, 2004; Storkel, Armbruster & Hogan, 2006): novel words with many similar sounding English words (i.e., dense neighborhood) are learned more quickly than novel words with few similar sounding English words (i.e., sparse neighborhood). The present study examined how neighborhood density influences word learning in native English-speaking adults learning Spanish as a foreign language. Students in their third semester of Spanish-language classes learned advanced Spanish words that sounded similar to many known Spanish words (i.e., dense neighborhood) or sounded similar to few known Spanish words (i.e., sparse neighborhood). In three word-learning tasks, performance was better for Spanish words with dense rather than sparse neighborhoods. These results suggest that a similar mechanism may be used to learn new words in a native and a foreign language.