Abstract: Adolescent egocentrism and its accompanying construct, imaginary audience ideation, are characteristic components of teen development. However, the introduction of social media has greatly altered the social landscape in which children grow up, creating a new form of audience for adolescents to consider. Previous studies have uncovered links between imaginary audience ideation and social media use in adolescent girls and young women, but researchers often fail to account for the unique attributes of the social media audience itself. The present study used a mixed methods design to explore social media audience ideation in 18–20-year-old women. Survey measures incorporated the novel Social Media Audience Scale to investigate social media audience ideation and its associations with social anxiety and social media usage time. Follow-up interviews allowed participants to elaborate on their experiences with social media both currently and during adolescence. Quantitative results revealed that 18–20-year-old women did display social media audience ideation, ranging in the frequency from rarely to sometimes. Furthermore, such ideation was positively associated with both social anxiety and social media usage time. Qualitative results provided insight into adolescent social media usage, indicating that young women maintain complex relationships with social media that evolve over time. This narrative data helped to further expand on quantitative findings.