Dispositional negativity—the tendency to experience more frequent or intense negative emotions—is a fundamental dimension of temperament and personality. Elevated levels of dispositional negativity have profound consequences for public health and wealth, drawing the attention of researchers, clinicians, and policymakers. Yet, relatively little is known about the factors that govern the momentary expression of dispositional negativity in the real world. Here, we used smart phone–based experience-sampling to demonstrate that the social environment plays a central role in shaping the moment-by-moment emotional experience of 127 young adults selectively recruited to represent a broad spectrum of dispositional negativity. Results indicate that individuals with a more negative disposition derive much larger emotional benefits from the company of close companions—friends, romantic partners, and family members—and that these benefits reflect heightened feelings of social connection and acceptance. These results set the stage for developing improved interventions and provide new insights into the interaction of emotional traits and situations in the real world, close to clinically and practically important end-points.