This longitudinal ecological momentary assessment study examined whether adolescents' use of social media to interact with peers relates to their experiences of social connectedness, social craving, and sensation seeking on an hourly level. Further, we investigated whether these associations differ for adolescents who were nominated by their peers as more or less susceptible to social influences, because highly susceptible youth may be more strongly impacted by social media due to heightened focus on peer behaviors and social feedback. The sample was 212 adolescents in the southeastern United States (M[subscript age] = 15 years; range 14 to 17; 56.2% female; 40% White, 28% Latinx, 26% African American, 15% mixed/other race). Controlling for both daily and between-subjects effects, we found a consistent pattern of hourly-level results that were robust to sensitivity analyses. When highly susceptible adolescents used social media to interact with peers in the last hour, they felt less socially connected to others and more strongly craved social connections and novel sensations. Youth who are particularly sensitive to social input from peers may feel less connected to others and crave more connections and exciting stimuli within 1 hr after using social media to interact with peers.