People with high perceived support have better mental health, but how this occurs is not well understood. We tested hypotheses from relational regulation theory that the main effect between perceived support and affect primarily reflects ordinary conversation and shared activity. In two studies (n = 193; n = 149), students rated three important network members and psychological reactions to each. In a third study (n = 72) strangers shared an activity in a round‐robin design. Affect was strongly determined by with who participants were interacting or thinking about. Perceived support, ordinary conversation, and shared activity were strongly linked, and each was related to high positive affect, low negative affect, perceived similarity, and few negative thoughts. Perceived support's link to affect emerged when strangers shared a brief activity. Thus, much of perceived support's main effect with affect could be explained as resulting from ordinary conversation and shared activity.