This study examined the concurrent relations of English (EL) and heritage language (HL) proficiency to executive functions (EF) among low-income dual language learners (DLLs) from immigrant families. In a sample of 90 children (age = 38-70 months) from Chinese-speaking Chinese American and Spanish-speaking Mexican American families recruited from Head Start preschools, children's EL and HL proficiency was assessed using receptive and expressive vocabulary tests, and EF was assessed using behavioral tasks measuring response inhibition and attention shifting. Multiple regressions were conducted to test the unique and interactive relations of EL and HL vocabulary to EF, controlling for family socioeconomic status and other demographic characteristics. Higher EL and higher HL vocabulary were uniquely associated with higher attention shifting. By contrast, neither EL nor HL vocabulary was uniquely associated with response inhibition. Interaction effects of EL × HL in relation to EF were also found. The results provided some evidence for the dual benefits of EL and HL proficiency on EF (especially attention shifting) among DLLs from low-income, immigrant families.