This study investigates the influences of process-based instruction (PBI) on students' self-regulated learning (SRL) strategy use in English as a foreign language (EFL) writing. Participants were 1521 fourth to sixth graders in Hong Kong primary schools. The students, in response to a questionnaire, reported that their English teachers used PBI at a high frequency in the classroom, while the students employed SRL strategies at a medium frequency. No significant differences in SRL strategy use were found across the three grade levels. Results of structural equation modelling (SEM) indicate that instruction at the before-writing stage had the strongest influence on the students' use of SRL strategies; instruction at the after-writing stage significantly impacted their use of self-initiating, self-monitoring and revising strategies; teaching writing at the while-writing stage had very little influence on the students' SRL strategy use. Implications for future research are discussed and suggestions for EFL teachers to improve their students' SRL strategy use in writing through PBI are included. Copyright © 2021 Elsevier Science Ltd.