This study investigated fast mapping in late-talking (LT) toddlers and toddlers with normal language (NL) development matched on age, nonverbal cognition, and maternal education. The fast mapping task included novel object labels and familiar words. The LT group performed significantly worse than the NL group on novel word comprehension and production, as well as familiar word production. For both groups, fast mapping performance was associated with concurrent language ability and later language outcomes. A post hoc analysis of phonotactic probability (PP) and neighborhood density (ND) suggested that the majority of NL toddlers displayed optimal learning of the nonword with low PP/ND. The LT group did not display the same sensitivity to PP/ND characteristics as the NL group.