Aims: This study investigated the efficacy of structured writing on reducing self-harm ideations and enhancing emotion regulation. Methods: Japanese university students (N=22) participated in the study. Participants were randomly assigned to the structured writing group (n=10; 70% female), or an assessment only control group (n=12; 67% female). For three consecutive days, participants in the intervention group performed structured writing that included psycho-education and self-reflection about emotions. The Self-Harm Ideation Scale, the Generalized Expectancy for Negative Mood Regulation Scale, and the Acceptance and Action Questionnaire-II were used to assess outcomes. Results: Structured writing had a short-term effect on expectancies for self-regulation of negative moods and acceptance of negative emotions, but had a limited effect on self-harm ideations. Conclusion: This study presents preliminary evidence that increasing awareness, learning, and reflection about emotions resulting from using a structured writing program is particularly useful for regulating emotions. J. Med. Invest. 64: 74-78, February, 2017