Objectives <p>Self-compassion, defined as a supportive attitude toward oneself in stressful circumstances, has an unclear impact on work engagement and related behaviors. This study aimed to examine the impact of self-compassion on work engagement and its mechanism via a cross-sectional study and a randomized controlled trial (RCT).</p> Method <p>Study 1 recruited 265 employees to complete online surveys measuring self-compassion, work engagement, psychological capital, and positive and negative affects, utilizing a cross-sectional design. Study 2, a RCT, involved 94 employees randomly assigned to an experimental group (mindfulness self-compassion coaching), an active-control group (relaxation and stress-reduction), or a no-intervention control group. Participants were assessed at baseline, post-intervention, and one month later using the same measures as Study 1.</p> Results <p>In Study 1, correlation and mediation analyses revealed that self-compassion positively predicted work engagement through the serial mediation of positive emotions and psychological capital. In Study 2, repeated-measures ANOVA showed that mindfulness self-compassion coaching significantly enhanced self-compassion, positive emotions, psychological capital, and work engagement, with sustained effects after one month. The development of self-compassion contributed to the improvement in work engagement, mediated by increased positive emotions and psychological capital.</p> Conclusions <p>These findings underscore the beneficial role of self-compassion in fostering work engagement from a positive psychology perspective and suggest group-based self-compassion coaching as a practical approach to enhance employees’ work engagement and mental well-being.</p> Preregistration <p>This research was pre-registered on the Open Science Framework (ID: <a href="https://doi.org/10.17605/OSF.IO/ACUN3">https://doi.org/10.17605/OSF.IO/ACUN3</a>).</p>