Written Corrective Feedback (WCF) is a controversial topic among theorists and researchers in L2 studies. Ellis, Sheen, Murakami, and Takashima (2008) identify two dominant dichotomies in this regard, that is focused vs. unfocused WCF and direct vs. indirect WCF. This study considered both dichotomies in a matrix format, resulted in the recognition of four types of operationally defined WCF, and aimed at: (1) investigating the effects of four types of WCF (i.e., focused direct CF, unfocused direct CF, focused indirect CF, and unfocused indirect CF) on intermediate EFL learners' writing performance; (2) finding out the most effective type of WCF for intermediate EFL learners' writing performance; (3) determining learners' attitudes toward the effectiveness of using WCF and the types which they had received. After conducting Nelson English Language Test (Test 300 D), out of 140 male and female Iranian EFL learners, 120 of them were selected as intermediate learners, aging from 14-18. The subjects were then assigned randomly to four homogeneous groups (each group including 30 participants). The pre-test and post-test both included a writing test which assessed learners' writing performance, and then their scores were analyzed by using analytic marking scale. The results indicated that, learners outperformed in all of the four groups, validating WCF as an effective technique which can be used in EFL classes. A clear implication of the study is that WCF types (specially unfocused direct CF) should be emphasized as an essential tool for developing writing ability of intermediate EFL learners.