While research into strategy-based instruction and language learning emotions has been thriving over decades as respective domains, research on how strategy-based interventions may influence learners' writing enjoyment has largely remained unexplored. Informed by (Positive Psychology) PP theories, this mixed-methods study aims to investigate the impact of strategy-based writing instruction on Chinese EFL undergraduates' writing enjoyment. The experimental group (N = 55) received a 6-step writing strategy teaching cycle, while the control group (N = 51) received conventional instruction focusing on linguistic knowledge. Participants' levels of writing enjoyment were assessed through pretest, immediate posttest, and delayed posttest questionnaires. Qualitative data from diaries and interviews provided further insights into the emotional factors at play. Results revealed that strategy-based instruction had a more lasting effect in increasing private enjoyment than traditional approaches. The study also explored the underlying factors contributing to emotional changes and the sources of writing enjoyment. These findings contribute to the field of strategy-based instruction and emotions, particularly in L2 writing and enjoyment, providing useful insights for classroom pedagogy.