The present study investigated the use of mobile dating apps for men who have sex with men (MSM), the privileging of masculinity in these online spaces, and related effects on attitudes about masculinity, the body, and the self. Using self-categorization theory as a framework, the study explored how men infuse masculinity/femininity and body language into their profiles in order to create symbolic boundaries between a masculine in-group and a feminine out-group, in the process further promoting an in-group bias for masculine partners. Findings indicated a clear preference for masculinity, both generally and in the form of the muscular male body. Drawing on selective self-presentation and the online disinhibition effect, the current work also investigated howpatterns of usage and personal attitudes impact photographic self-presentation, how the presence of face-disclosing and/or shirtless photos impact the use of language, and how visual self-presentation is related to demographic and attitudinal variables. The results indicated a connection between outness and face-disclosure, as well as between the amount of usage of MSM-specific mobile dating apps and face-disclosure. Men’s use of shirtless photos was significantly related to age, self-perceived masculinity, antieffeminacy attitudes, and drive for muscularity. Finally, priming theory was used to examine the relationship between MSM-specific mobile dating app usage and attitudes about men’s own and others’ masculinity/femininity and their bodies, as well as feelings of esteem and connectedness. Findings indicated connections between usage and self-perceived masculinity, internalized homonegativity, collective self-esteem, and body dissatisfaction, as well as social connectedness and anti-effeminacy attitudes for some men. Age, race, relationship status, education level, geographic location, and outness all served as important moderators. Constructions of gay masculinity have been associated with many issues, including risky sexual behavior, body dissatisfaction, disordered eating, lowered self-esteem, and racism. The current research advances our understanding of how MSM engage with masculinity/femininity and body language in a new media context, as well as the relationship between usage of MSM-specific mobile dating apps, psychosocial attitudes, personal feelings of esteem and connectedness, and photographic self-presentation strategies.