Previous research suggests that mindfulness and mind wandering are opposing constructs. However, little is known about why and how they are negatively related. Through a process-oriented approach, this cross-sectional study tested self-compassion and grit as mediators for the relation between mindfulness and mind wandering. A total of 487 self-identified meditators were recruited from the UK (241 female, 49.49%). Participants reported a mean age of 38.98 years (SD = 10.03), with an average of 2.26 h of meditation practice per week (SD = 4.47). Upon informed consent, the participants completed a self-report questionnaire that assessed the core variables under study. Path analysis indicated that mindfulness was related to self-compassion. Greater self-compassion was, in turn, related to greater grit, which was then related to lower mind wandering. Bootstrapping analysis further indicated that self-compassion and grit as mediators between mindfulness and mind wandering, above and beyond age, gender, hours of meditation, income, and education as covariates. The cross-sectional findings provided initial evidence of mediation by showing that mindfulness and mind wandering were related through self-compassion and grit.