This study investigated the immediate and sustained effects of revision-mediated (RICF) and attention-mediated (AICF) indirect coded corrective feedback on the written syntactic accuracy development of 50 upper-intermediate Iranian EFL learners assigned to two RICF and AICF groups. They received eight-session treatments, followed by an immediate posttest and then a delayed posttest after a four-week time interval. The collected written scripts were co-rated for syntactic accuracy by the researcher and her colleague. Descriptive and inferential statistical analyses were conducted with SPSS 21. The Wilcoxon Signed Rank Test and the paired-samples t-tests revealed that each treatment separately (i.e., revision-mediated and attention-mediated CF) had a statistically significant impact on EFL learners' written syntactic accuracy both in the short and long term. Moreover, the independent samples t-tests indicated no significant difference between the effects of revision-mediated and attention-mediated CF on EFL learners' written syntactic accuracy both in the short and long term. The paper provides discussion and implications.