Top-down and bottom-up reading processes have attracted attention from researchers in ESL/EFL teaching/learning. However, the role of these processes and their combination in L2 vocabulary learning and retention still needs further research. Given this, this study sought to consider their role in L2 vocabulary learning and retention by Iranian EFL learners. To this end, 100 intermediate participants were chosen from among a convenience sample of 180 EFL learners. They were then assigned to four random groups (Top-down, Bottom-up, Combined and Control). Finally, target vocabulary learning and retention were assessed by an immediate (learning) and delayed (retention) post-test. ANOVA results revealed that the bottom-up group outperformed the control group. The combined group also did better than the top-down and control groups on the post-test. However, the difference between the top-down and control group did not prove significant. In addition, the combined group surpassed the other groups in terms of the gain in mean scores. As for retention, both the bottom-up and combined processes resulted in the retention of the target vocabulary, with the former being even more effective. It can be suggested that these processes can be regarded as complementary factors in L2 vocabulary learning and retention.