Functional support-the availability of material aid, emotional support, or companionship-promotes general well-being. For men who have sex with men (MSM) living with HIV, having a person who supports you associates with viral suppression. This study examines the association between supportive partnerships and HIV viral suppression among middle-aged and aging MSM living with HIV. A total of 423 middle-aged and aging MSM (mean age, 58.2 years) from the Multicenter AIDS Cohort Study provided self-reported data about their partnerships. Separate Poisson regression models assessed how partnership type, support, strain, and duration from April 2017 were associated with repeated viral load measurements up to April 2019. Of the follow-up visits (N = 1289), 90.0% of participants were virally suppressed. Most participants reported being non-Hispanic White (61.0%) and college-educated (83.4%). Participants were asked about their primary partnerships (i.e., "someone they are committed to above anyone else") and secondary partnerships (i.e., those who can also be intimate or supportive but not necessarily romantic or sexual). The participants reported: no partnerships (45.2%), only primary partnerships (31.0%), only secondary partnerships (11.1%), or both primary and secondary partnerships (12.8%). Primary and secondary partnerships had mean (SD) durations of 15.9 (11.3) and 25.2 (16.5) years, respectively. Participants reporting both primary and secondary partnerships (compared with no partnership) showed significantly higher odds of being virally suppressed (adjusted prevalence ratio [aPR], 1.04; 95% CI, 1.00-1.08; p = 0.043). Albeit not statistically significant, primary-only (aPR, 1.01; 95% CI, 0.97-1.06; p = 0.547) or secondary-only (aPR, 1.03; 95% CI, 0.98-1.08; p = 0.224) partnership types were positively associated with viral suppression. Partner support and strain were not associated with viral suppression in any partnership group. Being older and non-Hispanic Black were positively and negatively associated with viral suppression, respectively. Encouraging partnerships should be considered one of clinicians' many tools to help middle-aged and aging MSM achieve long-term viral suppression.