In this study, the authors examined the impact of a vocabulary intervention designed to support vocabulary depth, or the building of semantic networks, in preschool children (n = 30). The authors further investigated the effect of specific instructional strategies on growth in vocabulary depth. The intervention employed shared book reading and guided play methods to teach words in conceptually linked categories, such as taxonomic and thematic groups. Using a within-subjects design, analyses indicated that the intervention had significant positive effects on children's depth of vocabulary knowledge. Children showed significantly greater growth in vocabulary depth for words taught in taxonomies as compared with words taught in themes. Three types of semantic information were learned more deeply for taxonomy words as compared with theme words: information about category membership, perceptual features, and object function. Results suggest that fostering deep vocabulary knowledge involves not only teaching single word entities but also introducing systems of conceptually related words to build semantic networks. [This article was published in "Reading Research Quarterly" (EJ1200818).]