Objectives <p>Brief, minimally guided, internet-delivered Mindfulness-Based Cognitive Therapy (iMBCT) formats may offer a scalable alternative, but evidence for their effectiveness and mechanisms remains limited. This pragmatic two-arm open trial evaluated the feasibility and preliminary effects of a 30-day asynchronous iMBCT program in a community sample. The primary outcomes were reductions in perceived stress and emotional distress; secondary analyses examined whether self-compassion and resilience functioned as processes of change.</p> Method <p>A total of 1348 adults reporting emotional distress were allocated to either the iMBCT program or a waiting list control (WLC). Due to high attrition, propensity score matching (PSM) was applied, yielding a final analytic sample of 190 individuals (91 iMBCT, 99 WLC). The intervention comprised six online MBCT sessions with audio-guided practices and psychoeducational materials. Outcomes (perceived stress, emotional distress, anxiety, depression, self-compassion, and resilience) were assessed at baseline and post-intervention using mixed-model ANOVA.</p> Results <p>Compared with WLC, the iMBCT group showed significant reductions in perceived stress (<i>ηp</i>² = 0.32, 95% CI [0.21, 0.41]), emotional distress (<i>ηp</i>² = 0.38, [0.28, 0.47]), anxiety (<i>ηp</i>² = 0.33, [0.22, 0.42]), and depression (<i>ηp</i>² = 0.34, [0.24, 0.44]), alongside increases in self-compassion (<i>ηp</i>² = 0.38, [0.27, 0.47]) and resilience (<i>ηp</i>² = 0.28, [0.17, 0.37]). Mediation analyses indicated that improvements in self-compassion and resilience partially accounted for reductions in stress and distress, explaining 18–32% of the total effect across outcomes. The intervention experienced 67% attrition, and engagement metrics were not collected.</p> Conclusions <p>A brief, asynchronous iMBCT program can reduce self-reported stress, emotional distress, anxiety, and depression while enhancing self-compassion and resilience in a community sample. However, high attrition, reliance on self-report, and the absence of clinical diagnoses or follow-up assessments limit generalizability and conclusions about long-term effects. Future studies should test such interventions in clinical populations, incorporate guided or synchronous elements to improve adherence, and collect objective engagement data to clarify dose–response relationships.</p> Preregistration <p>The study was not preregistered.</p>