This study evaluated the impact of the Spanish version of the Building Blocks software program and vocabulary on kindergarten mathematics outcomes. Participants included 270 Hispanic dual language learners from low-income communities. Relative to children in the computer assisted instruction (CAI)literacy control group, those in the Building Blocks CAI group evidenced higher posttest scores for Spanish mathematics, but not for English mathematics, after controlling for pretest numeracy. There were also main effects of English vocabulary and Spanish vocabulary predicting posttest mathematics scores in English and Spanish, after controlling for covariates. These findings support the use of the Building Blocks software as a supplemental method for improving the mathematics competencies of Hispanic dual language learners from low-income backgrounds.