Though mobile dating and hook-up apps show promise for circumventing historical barriers to partnering among sexual minority men (SMM), initial evidence suggests such app use may contribute to SMM’s relatively greater level of dissatisfaction with their bodies (Breslow et al., 2019) potentially via their exposure to discrimination online (e.g., Foster-Gimbel & Engeln, 2016). The present two studies were therefore developed to empirically examine the links between online sexual discrimination and the body image concerns of SMM using cross-sectional data gathered across two online surveys. In Study 1, three stable, single-factor measures assessing experiences of sexual racism, sexual femmephobia, and sexual sizeism were developed for use with SMM using exploratory factor analysis (n = 180). Predicted associations between these and validity measures provided initial convergent and divergent validity evidence in support of their use. This resulted in the retention of three novel 9-item measures of sexual discrimination. These measures were subsequently utilized in Study 2 (n = 530) to test a series of structural equation models that integrated elements of objectification and social comparison theory. Direct and indirect effects between app use variables, sexual discrimination, the internalization of appearance ideals, body surveillance, body shame, and body dissatisfaction were tested. Following model modifications, online sexual discrimination was found to be indirectly related to body dissatisfaction among SMM. The pathways by which this occurred varied by type of discrimination examined, with sexual racism related to dissatisfaction via the internalization of muscular ideals, and sexual femmephobia and sexual sizeism via the internalization of thinness ideals. App use behaviors were directly related to the reported frequency of sexual sizeism only and were not indirectly related to body dissatisfaction. Theoretical relationships among objectification theory variables were largely supported; however, a direct negative relationship between the internalization of muscular ideals and body dissatisfaction that had not been hypothesized also emerged as significant. The moderating potential of identity characteristics (e.g., racial identity, BMI) and appearance comparisons on tested relationships were examined. Higher levels of upward comparisons were found to strengthen relationships between body surveillance, internalization of thinness ideals, and body shame; all other moderation effects tested were non-significant.