Objectives <p>Past research has suggested that self-compassion fosters interpersonal functioning in Western samples. We extended previous findings by employing a longitudinal (Study 1) and a dyadic (Study 2) design in Japan. We hypothesized that self-compassion would predict higher relationship satisfaction and lower psychological intimate partner violence (IPV) beyond self-esteem.</p> Methods <p>Study 1 examined longitudinal associations using three-wave data across 6 months from 1,021 individuals involved in romantic relationships. Study 2 examined dyadic associations using cross-sectional dyadic data from 406 married couples. These participants completed the scales of self-compassion, self-esteem, relationship satisfaction, and psychological IPV perpetration (Study 1) and victimization (Study 2).</p> Results <p>A cross-lagged panel model in Study 1 indicated that self-compassion prospectively predicted lower psychological IPV perpetration (averaged <i>β</i> = -0.05). This model also revealed a bidirectional association between self-compassion (averaged <i>β</i> = 0.05) and relationship satisfaction (averaged <i>β</i> = 0.04). An actor-partner interdependence model in Study 2 indicated actor effects of self-compassion on own relationship satisfaction (<i>β</i> = 0.16, <i>p</i> &lt; 0.001) and psychological IPV victimization (<i>β</i> = -0.09, <i>p</i> = 0.04). Importantly, we found that actors’ self-compassion was positively associated with partners’ relationship satisfaction (<i>β</i> = 0.12, <i>p</i> = 0.02) and negatively associated with partners’ psychological IPV victimization (<i>β</i> = -0.19, <i>p</i> &lt; 0.001). These results were independent of self-esteem.</p> Conclusions <p>Self-compassion appears to help individuals have a satisfying relationship and avoid perpetrating psychological violence toward relationship partners in romantic and married couples in Japan.</p> Preregistration <p>This study is not preregistered.</p>