New mothers often show a reduction in exercise that can challenge their pre-motherhood exercise identity, an established exercise correlate. If they can adapt their exercise identity, they may accept their changed behavior and maintain some exercise; a healthy alternative to relentless pursuit or abandonment of their old identity. Identity theory lacks information about what predicts identity adaptation. Self-compassion, treating oneself kindly in the face of challenges, may promote identity adaptation; to our knowledge no research has examined this. This cross-sectional study examined the relationship between self-compassion and identity adaptation in a sample of 279 mothers of young children (Mage = 32.95, SD = 5.00) who identified with exercise and reported a reduction in exercise following motherhood (identity challenge). Participants completed online measures of self-compassion, positive reactions (acceptance, well-being, self-determined motivation), and negative reactions (guilt, shame, rumination, role conflict) in relation to their current relative to their pre-motherhood exercise. Regression analyses revealed that self-compassion related negatively to shame (ß = -.259, p <.001), rumination (ß = -.212, p < .001), and role conflict (ß = -.188, p = .002); and positively to acceptance (ß = .199, p = .001), well-being (ß= .426, p < .001), and self-determined exercise motivation (ß = .202, p = .001). Semi-partial correlations, controlling for self-esteem, found that self-compassion uniquely related to shame (r = -.259, p = .048), rumination (r = -.212, p = .013), and well-being (r = .426, p <.001). Self-compassion may help new mothers cope positively with exercise-related identity challenges.