Research on negative thinking and mental health has been criticized as focusing exclusively on trait like individual differences, and ignoring potential social influences. Nonetheless, little progress has been made in studying social influences. We tested a new theory of social support that hypothesizes that day-to-day social interaction helps regulate thought and affect. In two studies, students rated negative thinking and affect when thinking about their mothers, fathers, and closest peers. We isolated trait like negative thinking (i.e., stable across support providers) from socially influenced negative thinking (i.e., varied across support providers). There were significant social influences on each type of negative thinking such that the providers that elicited negative thinking also elicited worse affect and low perceived support, beyond recipients’ trait-like negative thinking. Some types of negative thinking were more trait like (worry and dysfunctional attitudes) and some were equally trait like and socially influenced (e.g., automatic negative thoughts).