This study investigates the effects of strategy-based instruction (SBI) on the promotion of learner autonomy (LA). LA was conceptualized and operationally defined as learner self-initiation and learner self-regulation. An intervention study was conducted with the participation of 37 students in an experimental group, and 54 students in two control groups at a Vietnamese university. An eight-week metacognition training package was incorporated into the academic writing programme of the experimental group. Students in the experimental group improved their ability to plan, monitor and evaluate a writing task more than students in the two control groups. Planning became the most often exercised skill, followed by evaluating and monitoring. Improvements in writing were maintained on a delayed test. Overall, the study suggests that strategy-based instruction in the form of training learners in task-specific metacognitive self-regulation improved learners' autonomy in both learning and their writing ability. (Contains 8 tables.)