Corpus concordancing has been utilized in second language (L2) writing classrooms for a few decades. Some studies have shown that this application is helpful, to a certain degree, to learners' writing process. However, how corpus concordancing is utilized for nonnative speakers' (NNSs) self error-correction in writing, especially the pattern of corpus consultation, has not been investigated. Previous studies has shown that learners were able to correct their errors with corpus consultation based on what their teachers had marked, but they did not recognize their errors by themselves. In this paper, the use of corpus concordancing is investigated for its effects on the error-correction process in essays, overall writing performance, and learners' attitudes. Three participants who were graduate ESL students were asked to write three essays which the prompts were chosen randomly from the TOEFL iBT essay-question database. Essay 1 was to assess their original writing competence; Essay 2 was a revised version of Essay 1 with the facilitation of corpus concordancing; and Essay 3 was written with corpus consultation. The findings showed that (1) during the error correction process, students had a certain pattern to revise errors with dictionaries and corpora. They made corrections to "word choice" the most in Essay 2 and prevented poor word choices in Essay 3. (2) As for the overall performance, Essay 3 was judged to be slightly better than Essay 2 better than Essay 1. (3) Students generally held a positive attitude toward the facilitation of corpus concordancing in writing and error correction. Even though the enhanced performance was not statistically significant, it is still worthwhile recommending the use of corpus concordancing to benefit students' writing and self error-correction.