Although entrepreneurs are said to have extremely stressful work, how they may be able to maintain their well-being in light of this is only poorly understood. Newly integrating the challenge-hindrance stressor framework with the stressor-detachment model of recovery from work stress, we investigate how specific challenge and hindrance stressors—cognitive and emotional demands—impact entrepreneurs' well-being by influencing their ability to detach and recover from work stress. Our diary study yielded 386 day-pair data points from 55 entrepreneurs. Challenge and hindrance stressors inhibited psychological detachment from work in the evening through increasing problem-solving pondering and work-related affective rumination, which diminished entrepreneurs' well-being the next morning. These effects are robust to alternative explanations (e.g., objectively measured sleep efficiency) and differ from relationships observed across entrepreneurs. Our findings elucidate the nature of stressors and the micro-foundational mechanisms of stress and recovery.