Across two studies, the current research investigated how different dimensions of narcissism (grandiosity/agentic extraversion, entitlement/self-centered antagonism, vulnerability/narcissistic neuroticism) relate to social networking site (SNS) use and behaviors. Study 1 employed a community sample of young adults, whereas Study 2 examined college students. Participants completed assessments of narcissism and SNS use through an online survey. Grandiosity/agentic extraversion was generally associated with greater levels of downward social comparison relative to the other two dimensions. Entitlement/self-centered antagonism generally showed weak correlations with SNS outcomes. Vulnerability/narcissistic neuroticism was generally associated with greater upward social comparison and perceived social exclusion relative to the other two dimensions. Results suggest that SNS experiences may vary depending on the dimensions of narcissism.