This study examined whether engaging episodic memory through autobiographical, narrative-based instruction enhances vocabulary learning and retention among adult English as a foreign language (EFL) learners, compared with semantic-based instruction and conventional rote learning. Fifty-four Iranian adult EFL learners (ages 20–35) were assigned to three groups (episodic, semantic, control). The episodic group learned target words through narrative vignettes designed to evoke personal experiences and emotional engagement, whereas the semantic group received structured meaning-focused instruction. The control group was taught through definition-based instruction with limited elaboration. Vocabulary knowledge was assessed using immediate and delayed (one-month) posttests. One-way ANOVAs revealed significant group differences on both the immediate posttest, F(2, 51) = 3874.49, p < 0.001, and the delayed posttest, F(2, 51) = 4747.34, p < 0.001. Although semantic instruction yielded higher retention than rote learning, episodic encoding produced the most durable gains. These findings suggest that embedding new lexical items in personally meaningful, context-rich experiences can substantially enhance short- and long-term vocabulary retention in adult EFL contexts. The results should be interpreted with caution due to the sample size and context-specific nature of the study.