The robust relation between maternal education and child language that is observed in monolingual populations has not been reliably replicated among bilingual children from immigrant families in the United States. We hypothesized that a variable that operates in immigrant populations--the language in which mothers achieved their highest level of education, is relevant to the benefits of maternal education to children's language growth. The participants were 92 U.S.-born bilingually developing children (47 boys, 45 girls) with native Spanish-speaking immigrant mothers. The mothers varied both in their level of education and in the language (English or Spanish) in which they had achieved their highest level of education. The children's expressive vocabulary in English and Spanish was assessed at 6-month intervals between 30 and 60 months. Four sets of multilevel models, which included estimates of children's relative amount of input in each language and mothers' age of arrival, found that maternal level of education in English was significantly related to children's English skill, but not their Spanish skill, and that maternal level of education in Spanish was related to children's Spanish skill, but not their English skill. These language specific relations between mothers' levels of education and their children's language development potentially explain previous findings in immigrant populations. These findings further argue that maternal education benefits children's language because education changes mothers' use of the language in which that education was achieved. There was no evidence of a language general benefit of education, as might arise from increased knowledge of child development.