Error treatment is one of the crucial factors in successful language learning; however, it is an important question if the feedback for error treatment should be provided implicitly or explicitly. The existing problems in the students’ pronunciation motivated the researchers to compare two types of corrective feedback, explicit vs. implicit, in treating learners’ phonological errors in terms of their immediate and delayed effects. For this purpose, the researchers selected 32 female participants in the upper-intermediate level English classes in Talash language institute located in Ghir out of 50 students through administration of The Certificate of Proficiency in English Speaking Test. The selected participants were randomly assigned into two groups. Both groups took a pronunciation pre-test and then one of the groups received explicit feedback; whereas the other group got implicit feedback. The participants’ probable progress was measured immediately after the treatment and one more time after a four-week delay. The collected data were analyzed by running independent samples t-tests on the pre-test and post-test scores. The results of the data analysis revealed that corrective feedback types, explicit and implicit, differ from each other in terms of their immediate and delayed effects on treating the participants’ phonological errors in favor of the explicit one. The results of this study could help language teachers, EFL learners, and also material developers in providing better conditions through selecting the best type of feedback on errors for learning English pronunciation and treating phonological errors.