Sex is rarely discussed in theories of well-being and rarely empirically examined using methods other than cross-sectional surveys. In the present study, a daily diary approach was used (for 21 days with 152 adults) to explore the relationship between the presence and quality of sexual episodes and well-being (positive affect, negative affect, meaning in life). Time-lagged analyses demonstrated that sexual activity on 1 day was related to greater well-being the next. As for the quality of episodes, higher reported sexual pleasure and intimacy predicted greater positive affect and lower negative affect the following day. When the reverse direction was tested, well-being did not predict next-day sexual activity, pleasure, or intimacy. These results suggest a unidirectional relationship in which the presence and quality of sexual activity lead to gains in well-being the following day. Contextual moderators (gender, relationship status, relationship closeness, and relationship length) allowed for tests of conditions altering the link between sexuality and well-being. Relationship closeness was the most robust moderator in predicting greater levels of meaning in life and positive affect following sexual episodes. These data provide evidence to support the continual consideration of sex in empirical work and theoretical models of elements that comprise healthy relationships and a good life.