AbstractVocabulary knowledge of young children, as a well-established predictor of later reading comprehension, is an important domain for assessment and intervention. Standardized, knowledge-based measures are commonly used by speech-language pathologists (SLPs) to describe existing vocabulary knowledge and to provide comparisons to same-age peers. Process-based assessments of word learning can be helpful to provide information about how children may respond to learning opportunities and to inform treatment decisions. This article presents an exploratory study of the relation among vocabulary knowledge, word learning, and learning in vocabulary intervention in preschool children. The study examines the potential of a process-based assessment of word learning to predict response to vocabulary intervention. Participants completed a static, knowledge-based measure of vocabulary knowledge, a process-based assessment of word learning, and between 3 and 11 weeks of vocabulary intervention. Vocabulary knowledge, performance on the process-based assessment of word learning, and learning in vocabulary intervention were strongly related. SLPs might make use of the information provided by a process-based assessment of word learning to determine the appropriate intensity of intervention and to identify areas of phonological and semantic knowledge to target during intervention.