The goal of the current study is to explore the influence of knowledge on socioeconomic discrepancies in word learning and comprehension. After establishing socioeconomic differences in background knowledge (Study 1), the authors presented children with a storybook that incorporates this knowledge (Study 2). Results indicated that middle-income children learned significantly more words and comprehended the story better than lower-income children. By contrast, Study 3 presented children with a novel category and found that children performed equally in their word learning and comprehension. This suggests that socioeconomic differences in vocabulary and comprehension skills may be partially explained by differences in extant knowledge.