Investigations have been too limited and inconclusive to find out whether written corrective feedback improves grammatical accuracy of learners. This study aimed at investigating the comparative effects of direct and indirect corrective feedback on short-term and long-term retention of the subject-verb agreement by Iranian EFL writers. The design of the study was a two group pre-post-test quasi-experimental one. The Participants were 45 male and female learners at the age range of 14 to 16. Their L1 was Turkmen and they were all taking an elementary course at a language school in Gonbad Kavoos, Iran. The participants were assigned to two experimental groups i.e. direct and indirect feedback groups, and one control group. To collect data, a pretest, post-test and a delayed post-test were given to all the groups. One-way Analysis of Variance (ANOVA) was run to test the research hypotheses. The results showed that the types of corrective feedback did not have a significant positive effect on the participants' short-term and long-term retention of subject-verb agreement. Besides, Scheffe post hoc test showed that there was a significant decline in grammatical accuracy of the indirect feedback group in the delayed posttest. The results have some implications for teaching writing in the EFL context.