Background: Marital status rates may have changed over time in prostate cancer (PC) patients and may have affected cancer-specific mortality (CSM) and other-cause mortality (OCM). Methods: Within the Surveillance, Epidemiology, and End Results database (2004–2015), we identified PC patients who were either married (n = 326,664) or unmarried (n = 106,533). Temporal trends, cumulative incidence plots, as well as multivariable competing risks regression analyses focused on (1) the overall population, (2) D'Amico low-risk N0M0 PC, (3) D'Amico intermediate-risk N0M0 PC, (4) D'Amico high-risk N0M0 PC, (5) N1M0 PC, and (6) M1 PC patients. Results: Of all, 24.6 % were unmarried and increased trend over time (23.0%–26.9%, P <0.001). Unmarried men experienced higher CSM rates (9.8% vs. 6.3% in married men, P <0.001) and OCM rates (24.3% vs. 17.1% in married men, P <0.001) in the overall population, as well as in all subgroup analyses. Unmarried status represented an independent predictor of higher CSM (hazard ratio: 1.19, P <0.001) and OCM (hazard ratio: 1.41, P <0.001) in the overall cohort, as well as in all subgroup analyses except for the N1M0 subgroup, where marital status did not reach independent predictor status for CSM. Conclusions: Unmarried PC patients are at higher risk of CSM and OCM. This relationship applies to all stage subgroups, except for the N1M0 subgroup. Consequently, unmarried individuals should ideally benefit of improved counseling, closer follow-up, as well as of other measures aimed at reducing the CSM and OCM disadvantages. © 2019 Elsevier Inc.