Though the influences of syntactic and semantic regularity on novel word learning are well documented, considerably less is known about the influence of phonological regularities on lexical acquisition. The influence of phonotactic probability, a measure of the likelihood of occurrence of a sound sequence, on novel word learning is investigated in this study. Thirty-four typically developing children (from ages 3 years 2 months to 6 years 3 months) participated in a multitrial word-learning task involving nonwords of varying phonotactic probability (common vs. rare) paired with unfamiliar object referents. Form and referent learning were tested following increasing numbers of exposures (1 vs. 4 vs. 7) and following a 1-week delay. Correct responses were analyzed to determine whether phonotactic probability affected rate of word learning, and incorrect responses were analyzed to examine whether phonotactic probability affected the formation of semantic representations, lexical representations, or the association between semantic and lexical representations. Results indicated that common sound sequences were learned more rapidly than rare sound sequences across form and referent learning. In addition, phonotactic probability appeared to influence the formation of semantic representations and the association between semantic and lexical representations. These results are integrated with previous findings and theoretical models of language acquisition.