Although machine translation (MT) is generally unwelcome in lessons, especially in academic contexts, recent research shows that MT can help learners improve the quality of their writing in a second language (L2). However, previous research has not sufficiently clarified whether learning from modifications supplied by MT has long-term effects on students’ grammatical accuracy and lexical depth and breadth. Further, concerning this potential contribution to learning, research with advanced second-language learners is lacking. Therefore, this study aims to clarify the outcomes of feedback from MT on the writing of academic essays by 12 upper-intermediate and advanced Chinese learners of English in Japan and the USA. The kinds of revisions learners made to their first drafts with MT help are clarified. Further, the influence of MT on follow-up writing assignments and participants’ impressions before and after its use are examined. Results indicate that MT can help learners make progress not only in various aspects of linguistic forms but also beyond the sentence level. Overall, findings suggest that, in order for second-language learners to develop the ability to use their L2 more accurately, MT can be effectively employed in the classroom.