Nowadays, the function of language teaching and testing has been paid much attention by researchers. There is an overall notion in the literature that motivation, as driving force, is one of the likely learners' traits. The aim of this study was to examine the comparative impact of self-assessment and teacher-assessment on learners' academic motivation. The participants were 60 intermediate students in two groups at Novin-Rezvan Foreign institute. At the beginning of semester, the instructor gave a motivation questionnaire as pre-test to the students, and then both groups were put to the similar content and instructional method for reading strategies. There was only one difference, i.e., the students in the experimental group self-assessed themselves, whereas the students in another group were assessed by the teacher-assessment. At the end of treatment session, a post-motivation questionnaire was given to the students to assess level of their motivation. Two t-tests were run, and the results showed that self-assessment play an important impact on Iranian EFL learners' academic motivation.