This study examined how the narrative construction of intimacy and affect in relationship stories predicted individuals’ relationship quality, stability, and mental health. A purposive national sample of 150 individuals in long-term relationships wrote stories about four key relationship events and completed measures of relationship quality and mental health. Stories were analyzed for narrative and linguistic indicators of intimacy-related and affective content. Intimacy-related content was positively associated with relationship quality and mental health. Linguistically-coded affect was not associated with any outcomes. The most robust predictor of relationship quality and mental health was the narratively constructed affective tone of relationship story endings. The narrative construction of positive story endings significantly increased the likelihood of participants remaining together with their partners over time.