This study examines the influence of a parent workshop intervention on vocabulary acquisition of at-risk preschool children during parent-child shared storybook reading. Sixty-nine parents were randomly assigned to either treatment or control group. In the treatment condition, parents were taught to implement elaborated vocabulary instruction (definitions, synonyms, and examples) and non-elaborated vocabulary instruction (simple definitions only) during shared storybook reading (SSR). In the control group (stories only), parents read the same storybooks as the treatment families but did not provide direct vocabulary instruction. Children's vocabulary learning was assessed using a researcher-designed assessment, Big Words for Little People (BWLP), at three time points during the study: before, after, and 14 days following the end of the intervention. The results suggest that meaningful explanations of unfamiliar words during parent-child shared storybook reading may be a viable strategy for fostering vocabulary learning, which is critical for later reading achievement.