This study examined relationship status (e.g., single versus not single) and number of sexual partners in relation to muscularity- and disordered eating-related attitudes and behaviors among 1090 cisgender gay men enrolled in The PRIDE Study in 2018. Participants completed measures assessing muscle dysmorphia (MD) symptoms, disordered eating attitudes and behaviors, and appearance- and performance-enhancing drug or supplement (APEDS) use. In linear regression models adjusting for theoretically relevant covariates, neither relationship status nor number of past-month sexual partners was associated with disordered eating attitudes. In terms of MD symptoms, single (versus not single) relationship status was associated with greater appearance intolerance, and a greater number of sexual partners was associated with greater drive for size and functional impairment. In adjusted logistic regression models, a greater number of past-month sexual partners was associated with use of anabolic-androgenic steroids, synthetic performance-enhancing substances, protein supplements, and creatine supplements, as well as greater likelihood of engaging in compelled/driven exercise. Across all associations, effect sizes were generally small. Overall, results support that inquiring about sexual partners may have utility in evaluating risk for muscularity-oriented attitudes and behaviors among cisgender gay men. Future work will need to replicate these findings, particularly in more diverse samples.