Purpose: To investigate whether phonological or semantic encoding cues improved the fast mapping or word learning performance of preschoolers with specific language impairment (SLI) or typical development (TD) and whether performance varied for words containing high- or low-frequency sublexical sequences that named familiar or unfamiliar objects. Method: Forty-two preschoolers with SLI, 42 preschoolers with TD matched for age and gender to the children with SLI, and 41 preschoolers with TD matched for expressive vocabulary and gender to the children with SLI learned words in a supported learning context. Fast mapping, word learning, and post-task performance were assessed. Results: Encoding cues had no effect on fast mapping performance for any group or on the number of words children learned to comprehend. Encoding cues appeared to be detrimental to word production for children with TD. Across groups, a clear learning advantage was observed for words with low-frequency sequences and, to a lesser extent, words associated with an unfamiliar object. Conclusion: The results suggest that phonotactic probability and previous lexical knowledge affect word learning in similar ways for children with TD and SLI and that encoding cues were not beneficial for any group.