This study investigated the relationship between learner autonomy (LA) and indirect written corrective feedback (IWCF) in an EFL writing classroom in Vietnam. Forty-one intermediate EFL learners from a class of a foundation writing course volunteered to participate in the study. During the course, the teacher provided IWCF in response to the learners' errors and encouraged them to revise, edit, and correct those errors using a set of procedures. The study revealed that the learners with higher autonomy were more successful in correcting errors and in producing error-free modified pieces of writing than those with lower autonomy. This indicated that there could be a considerable mediating effect of LA on the efficacy of IWCF. It was also found that there seemed to be positive changes in the awareness and learning practices of the learners towards a more autonomous learning at the end of the course. The study suggests that IWCF can be very effective in an autonomy-supportive learning environment and that IWCF could help EFL learners to be more autonomous in language learning. Various implications are also discussed.