Abstract The study aimed at investigating the efficacy of written corrective feedback (CF) in improving Iranian EFL learners’ grammatical accuracy. It compared the effects of focused and unfocused written CF on the learners’ grammatical accuracy. 75 EFL students formed a one control and two experimental groups. The focused feedback group was provided with error correction in tenses. The unfocused feedback group was provided with error correction in tense, articles, spelling, pronouns, vocabulary, and prepositions. The results indicated a significant improvement in accuracy for the two experimental groups from pretest to posttest. The outcomes demonstrated that giving written CF was effective, which enhanced learners' grammatical accuracy, and that focused and unfocused written CF were not of differential significant effect in such manner. The results on the construct of the attitudinal questionnaire indicated learners’ preference in two experimental groups for the interactional activities, error correction, and the different type of CF techniques. The mean scores on each content area of the questionnaire suggested that learners in the focused group scored higher than the other groups in their attitudes toward the errors to be corrected. Manuscript profile