People who identify with exercise verify their identity through exercise engagement and experience negative affect if they fail to behave in accordance with their identity. Identity theory posits that negative affect should motivate identity-consistent exercise. This link is not established, and other behaviour change theories suggest negative affect can thwart goal pursuits. Self-compassion (SC) is the tendency to relate to oneself with support and is associated with tolerance of negative emotions. SC may moderate the relationship between any negative emotions exercisers experience when they behave inconsistently with their exercise identity and both their exercise intensions and perceptions of exercise identity-behaviour consistency. We examined this possibility in a week-long, online, prospective study where 274 exercisers who had recently failed to engage in sufficient exercise to verify their identity completed measures of demographics, SC, negative emotions (state shame and guilt) and indicated their exercise intentions for the following week. One week later, exercisers reported the extent to which their past week’s exercise aligned with their identity standard on a scale of 0% to 100% (i.e., identity-behaviour consistency). SC moderated the relationship between state guilt and identity-behaviour consistency (p < .029) such that guilt was positively associated with identity-behaviour consistency for those high in SC but negatively related to identity behaviour consistency among those low in SC. No other moderated relationships were significant. People who are self-compassionate may cope better with feelings of guilt, and instead of becoming paralyzed by guilt, use this emotion as a force to motivate behaviour change.