This study examines how learners’ proficiency levels influence the concreteness effect in vocabulary learning within the context availability theory. A total of 178 Korean EFL university students were divided into beginner, intermediate, and advanced groups. Participants completed vocabulary tasks under two conditions—isolated word and contextualized sentence—to assess the role of context. Immediate and delayed post-tests measured short- and long-term retention. Target words were categorized as concrete or abstract based on concreteness ratings, and a repeated-measures ANOVA tested main effects and interactions. Results showed a strong concreteness effect in both testing sessions, influenced by proficiency level. However, sentence-level contextual information did not significantly enhance learning, and even appeared to hinder performance in the immediate post-test, offering limited support for context availability theory in short-term memory. In the delayed post-test, a weak three-way interaction emerged: beginner and intermediate learners displayed reduced concreteness effects under the contextual condition, suggesting that context aided abstract word learning and partially supported the theory in long-term memory. Overall, the findings indicate that the concreteness effect is moderated by learner proficiency and that the benefits of contextual information depend on both lexical properties and individual learner characteristics.