This study compared the effects of semantically related and unrelated word lists on Iranian EFL learners' short-term and long-term vocabulary recognition and retention. Sixty elementary students were divided into experimental and control groups. The experimental group learned words from semantically related lists while the control group learned from unrelated lists. Immediate and delayed vocabulary tests showed that the control group performed better on the immediate test, while the experimental group performed significantly better on the delayed test. The results suggest that semantically related word lists may facilitate better long-term vocabulary retention compared to unrelated lists.