A compelling body of evidence suggests that EFL students have problem with logical connectors' appropriate use in writing. This study explored Iranian EFL students' adversative connectors use in their essay writing course. To this end, a Learner Corpus of 60393 words consisting of 156 essays was compiled. LOCNESS was chosen as the criterion corpus. AntConc, a freeware concordance program, was used to analyze the data. The findings revealed that, in general, learners underused adversative connectors; both native and non-native students used "but" the most; "on the other hand," and "while" were overused and "despite," "yet," and "instead" were underused by the learners suggesting that the top five most overused adversative connectors make up around 72% of learners' adversative connector use indicating that learners tend to use the same adversative connectors at the cost of underusing the other ones. Analysis of concordance line also illustrated that the learners tended to misuse the subordinating conjunction whereas and though in the initial position. It seems that learners need to be taught how to distinguish between different types of adversative connectors and how to use a wider variety of adversative connectors to reach a better coherence and cohesion in their writings.