The purpose of this study is to examine whether supportive interactions on social networking sites mediate the influence of SNS use and the number of SNS friends on perceived social support, affect, sense of community, and life satisfaction. Employing momentary sampling, the current study also looked at the relationship between supportive interaction and immediate affect after the interaction over a period of 5 days. An analysis of 339 adult participants revealed a positive relationship between supportive interaction and positive affect after the interaction. A path model revealed positive associations among the number of SNS friends, supportive interactions, affect, perceived social support, sense of community, and life satisfaction. Implications for the research of online social networking and social support are discussed. 2013 Elsevier Ltd. All rights reserved.