Purpose: The goal of this study was to provide guidance to clinicians on early benchmarks of successful word learning in an interactive book reading treatment and to examine how encoding and memory evolution during treatment contribute to word learning outcomes by kindergarten children with specific language impairment (SLI). Method: Twenty-seven kindergarten children with SLI participated in a preliminary clinical trial using interactive book reading to teach 30 new words. Word learning was assessed at 4 points during treatment through a picture naming test. Results: The results indicate that the following performance during treatment was cause for concern, indicating a need to modify the treatment: naming 0-1 treated words correctly at Naming Test 1; naming 0-2 treated words correctly at Naming Test 2; naming 0-3 treated words correctly at Naming Test 3. In addition, the results showed that encoding was the primary limiting factor in word learning, but memory evolution also contributed (albeit to a lesser degree) to word learning success. Conclusion: Case illustrations demonstrate how a clinician's understanding of a child's word learning strengths and weaknesses develop over the course of treatment, substantiating the importance of regular data collection and clinical decision-making to ensure the best possible outcomes for each individual child.