Written corrective feedback for improving L2 writing skills has been a debatable issue for more than two decades. The aims of this meta-analysis are to (1) provide a quantitative measure of the effect of computer-generated written feedback for improving L2 writing skills and (2) verify how moderators (i.e., adopted technology, task types, and learners' language proficiency) mitigate the effectiveness of corrective feedback provided by computer technology for developing the L2 students' writing fluency and accuracy. A comprehensive search was performed to collect the population of computer-mediated corrective feedback (CMCF) studies. The effect sizes were calculated for 14 primary studies with L2 participants (N = 1220). The findings indicate a large overall effect of CMCF (d = 1.21). A medium overall effect was found in using automated writing evaluation (AWE) technology for writing skills, whereas a large effect size was determined in using non-AWE technology. The results further indicate a large overall effect in using CMCF for both writing fluency and accuracy. As for the proficiency level of moderators, the results indicate a large overall effect in using CMCF among beginners and intermediate learners, whereas the overall effect is small among advanced learners. Limitations and recommendations for future studies are also raised in this study.