Socioeconomic status (SES) has been repeatedly linked to the developmental trajectory of vocabulary acquisition in young children. However, the nature of this relationship remains underspecified. In particular, despite an extensive literature documenting young children's reliance on a host of skills and strategies to learn new words, little attention has been paid to whether and how these skills relate to measures of SES and vocabulary acquisition. To evaluate these relationships, we conducted two studies. In Study 1, 205 2.5- to 3.5-year-old children from widely varying socioeconomic backgrounds were tested on a broad range of word-learning skills that tap their ability to resolve cases of ambiguous reference and to extend words appropriately. Children's executive functioning and phonological memory skills were also assessed. In Study 2, 77 of those children returned for a follow-up session several months later, at which time two additional measures of vocabulary were obtained. Using Structural Equation Modeling (SEM) and multivariate regression, we provide evidence of the mediating role of word-learning skills on the relationship between SES and vocabulary skill over the course of early development.