This study deals with spotting the grammatical errors committed by the Iranian students majoring in English translation while translating the Persian sentences into English and investigating the effect of two teaching methods, including Grammar-Translation Method (GTM) and Communicative Language Teaching Method (CLT), on minimizing these errors. For this purpose, the grammatical errors in the translation of thirty students were identified. These errors were analyzed and classified according to Keshavarz’, s model of error analysis. The students were divided into two groups,the first group received the learning materials based on GTM, and in the second group CLT was applied. Afterward, a test which included English sentences extracted from Modern English 1 and 2 was designed based on the errors taken from the corpus compiled by the students’,translations. Then the frequency of the errors in both groups were analyzed by SPSS software to determine the significance of using these methods on minimizing the grammatical errors made by the students in their translations into English. To determine the level of significance, the probability value was calculated for raw errors, GTM and CLT errors. The analysis of Pearson correlation showed that both methods had their significance,however, the communicative method proved to be slightly more effective than the other. Undoubtedly, this does not mean to underestimate the efficacy of grammar translation method since it seems that it plays a complementary role in teaching environment, and achieving better pedagogical results cannot be prescribed on a single method.