Abstract: Most Americans aged 18–49 use social media ( Atske, 2021 ). The social compensation ( McKenna & Bargh, 2000 ) and social enhancement ( Kraut et al., 2002 ) hypotheses offer two frameworks for understanding online social behavior, yet the evidence for these hypotheses is mixed. Two factors that may be important to consider in the context of online social behavior are social anxiety symptoms ( Weidman et al., 2012 ) and perceived social support ( O’Day & Heimberg, 2021 ). This study aimed to understand how online social behavior may be associated with social anxiety and perceived social support. Participants ( N = 303) completed self-report measures of social anxiety symptoms and perceived social support, as well as a task designed to simulate online social interactions. Participants who mentioned social activities in a mock social media profile had significantly lower social anxiety and significantly higher perceived social support than those who did not. There were no significant associations between social anxiety or perceived social support and the number of people with whom participants expressed interest in interacting. Participants with higher perceived social support indicated that they wanted to maximize their chances of interacting with another person. Overall, these findings provide some support for the social enhancement hypotheses. Further research is needed to disentangle how social anxiety and perceived social support may be relevant to online social behavior.