We conducted two studies to examine the effects of an interactive read aloud and vocabulary intervention on the vocabulary knowledge of Spanish-speaking preschoolers living in the U.S. In Study 1, 68 children (n = 34 in the treatment group) and 6 parents in the treatment group received the intervention in Spanish at home, and in Spanish and English in the preschool. Results indicated a significant effect of the intervention on children's receptive and expressive vocabulary knowledge in Spanish favoring the treatment group. Effect sizes were moderate to large. English outcomes were significant for the treatment group only on the receptive vocabulary measure. Children who participated in the Home plus Preschool intervention (n = 6) made significant gains on their Spanish vocabulary knowledge with large effect sizes. In Study 2 we conducted a single subject design study with four preschool children and their mothers. The intervention was provided at home. Results indicated a change from baseline to maintenance for all four children on their Spanish vocabulary knowledge. Parents in both studies saw important changes in their children's engagement in read alouds as well as in their children's communication skills.