In recent years, MT has shown a marked increase in popularity among L2 students, both inside and outside the classroom. While MT is a smart tool to assist L2 learners’ writing, ‘smart’ strategies are also crucial for learners to effectively use MT for their language learning. Studies have confirmed that learners’ attitudes and strategies for utilizing and adopting options from resources during their writing and revising vary. In the similar vein, it is assumed that students utilize different strategies when using MT, which will influence their writing outcomes. Despite the growing number of students using MT, learner strategies for using MT have not been reported. Therefore, the current study investigated L2 learners’ strategies for using MT during the writing and revising process. The present study employed a mixed method with quantitative content analysis of the 32 Korean college students’ essays and screen recordings of their writing processes and qualitative analysis of post-interviews. The result showed that the students were not merely dependent on MT during writing, but they effectively and strategically used MT for their needs based on their linguistic knowledge and other resources. However, the study also showed that depending on language proficiencies, the students perceived using MT differently and used it in different ways. While more proficient students perceived MT as a smart CALL tool, using MT was too challenging for low-level students. Based on the results, the study suggested pedagogical implications regarding using MT in language classrooms.