This paper focuses on the effects of gender diversity – in terms of binary- and third-gender – on social media engagement (SMEn). Specifically, we examine the extent to which SMEn's antecedents and outcomes vary between binary- and third-gender people. Based on the uses and gratification theory (UGT), we develop and validate a model using two cross-sectional studies. Data have been collected from heterosexual and third-gender people (TGP) separately, and analysed with the structural equation modelling (SEM) technique. Our results show that the incentives and outcomes of SMEn are not identical across different gender groups; rather, socially excluded TGP take advantage of social media differently than their heterosexual counterpart. More specifically, habit is the strongest predictor of SMEn for the heterosexual group, which is emotional reassurance for the TGP. Interestingly, identity management is an important determinant of SMEn only for TGP, while social interaction is important for both groups. We further find that SMEn enhances both groups' quality of life and social self-esteem but more for TGP. This study advances knowledge by applying UGT in a new research setting within information systems. The findings provide guidelines to social media architects and policymakers on engaging socially disadvantaged people with social media and enhancing their social wellbeing.