We conduct a cluster-randomized evaluation of an early literacy intervention that provided Kenyan parents with illustrated children's storybooks and modified dialogic reading training.  Rural communities were randomly assigned to treatment or control.  Within treatment communities, households were further randomized to receive children's storybooks in either Luo (the mother tongue of all children in the sample) or English (a national language, and the primary language of instruction in grade 4 of primary school and beyond).  We estimate the impacts of treatment on children's vocabulary and literacy skills. Mother tongue storybooks improved early literacy among school-aged children, but neither treatment improved pre-literacy skills among the preschool-aged children targeted for the program.