The present study attempted to probe the effectiveness of online learning on Iranian EFL learners' self-concept. It also analyzed the effect of online learning on the EFL learners' writing achievement. To do this, a total number of 50 students of pre-intermediate level was selected based on available sampling. A pre-test of writing was administered to the participants at the beginning of the term to ensure that they had the same language background. Then, they were randomly assigned as experimental and control group (25 Ss in each group). Experimental group benefited from online learning through BBB, and other group with the same number of students regarded as control group and received conventional method of teaching. At the beginning of the term, pre questionnaire of self-concept published among students of EG. The research was done in eight sessions and in the last session, post-test of writing was assigned to both groups to determine whether online learning method had positively affected the EFL learners' achievement and their self-concept. Moreover, post questionnaire of self-concept was published among experimental group to analyze their self-concept in online learning context. Data analysis of tests and questionnaire revealed that online learning method had positive effect on the EFL students' writing achievement and their self-concept. It is hoped that the results of the research indicate the importance of online learning through the mentioned application in the educational system. تفاصيل المقالة