The purpose of this exploratory study was to examine the longitudinal, bidirectional relations between receptive and expressive Spanish and English language and internalizing and externalizing behavior problems in a sample of 97 preschool children from Spanish-speaking, homes who were enrolled in a Head Start program. Eight cross-lagged path models were conducted: four for each language. Models tested the autoregressive and cross-lagged paths between two dimensions of language (expressive and receptive) and behavior problems (internalizing and externalizing) over the preschool year. Findings highlight the critical importance of the home language for children who are dual language learners and suggest programs ensure adequate home language support is available in the classroom. Future directions are discussed. (author abstract)