BACKGROUND: Little is known about the effects of disclosure of HIV-serodiscordant relationships on clinical outcomes. We aimed to evaluate the effect of relationship disclosure on HIV viral suppression, and hypothesized that disclosure by HIV-positive and HIV-negative partners would be associated with viral suppression in the HIV-positive partner. METHODS: We conducted a Canadian national online and telephone-administered survey of HIV-positive and HIV-negative partners in serodiscordant relationships. The primary outcome was self-reported viral suppression. Multivariable analyses were undertaken using Firth logistic regression. RESULTS: We recruited 540 participants in current serodiscordant relationships (n = 228 HIV-negative; n = 312 HIV-positive). Similar proportions of HIV-positive and HIV-negative partners disclosed their relationship to healthcare professionals (82% v. 76%, p = 0.13). Among HIV-positive partners, disclosure of the relationship to healthcare professionals increased the odds of viral suppression (aOR = 4.7; CI: 2.13, 10.51) after adjusting for age, education, and relationship turmoil due to HIV. Increasing age (aOR = 1.28; 95% CI = 1.07, 1.55) and education (aOR = 2.43; 95% CI = 1.15, 5.26) were also associated with viral suppression. Among HIV-negative partners, relationship disclosure was not associated with viral suppression and HIV-negative heterosexual men were less likely to report that their HIV-positive partners were virally suppressed (aOR = 0.24; CI: 0.09, 0.61). CONCLUSIONS: Disclosure of HIV-serodiscordant status by HIV-positive participants to healthcare professionals was associated with increased odds of viral suppression. Similar effects were not evident among HIV-negative participants. Future work should explore factors that empower relationship disclosure and incorporate them into supportive services for HIV-serodiscordant relationships.