Objectives <p>Numerous studies have focused on the ways to cultivate self-compassion (SC). Most of the SC interventions were typically lengthy and did not capture momentary fluctuations in SC after each exercise in the intervention. Therefore, we explored the impact of repeated self-compassionate writing as an ecological momentary intervention (EMI).</p> Method <p>Seventy-five participants completed a 3-week study with signals sent twice daily, resulting in 1,980 observations collected. During the 1-week control period, participants were asked to report their experiences of negative events, momentary SC, and momentary stress. In the subsequent 1-week intervention period, they engaged in SC writing whenever they experienced negative events. Trait SC and weekly stress were also evaluated before and after the intervention, including a 1-week follow-up period.</p> Results <p>Multilevel modeling showed a slight significant&#xa0;increase in momentary SC and a reduction in momentary stress. However, the slope did not differ significantly between the intervention and control periods. Moreover, there were no significant changes in trait SC nor in weekly stress, although the weekly stress levels showed a decreasing trend with a small effect size from pre to post intervention.</p> Conclusions <p>This study provided preliminary evidence of the feasibility and utility of EMI in cultivating SC using repeated self-compassionate writing. Although the effect sizes were small, the study highlighted possible approaches to increase the effectiveness of the intervention.</p> Preregistration <p>This study is not preregistered.</p>