Background To reduce the increasing burden of pneumonia hospitalizations, we need to understand their determinants. Being married may decrease the risk of severe infections, due to better social support and healthier lifestyle. Patients and methods In this population-based case-control study, we identified all adult patients with a first-time pneumonia-related hospitalization between 1994 and 2008 in Northern Denmark. For each case, ten sex- and age-matched population controls were selected from Denmark’s Civil Registration System. We performed conditional logistic regression analysis to estimate the odds ratios (ORs) for pneumonia hospitalization among persons who were divorced, widowed, or never married, as compared with married persons, adjusting for age, sex, 19 different comorbidities, alcoholism-related conditions, immunosuppressant use, urbanization, and living with small children. Results The study included 67,162 patients with a pneumonia-related hospitalization and 671,620 matched population controls. Compared with controls, the pneumonia patients were more likely to be divorced (10% versus 7%) or never married (13% versus 11%). Divorced and never-married patients were much more likely to have previous diagnoses of alcoholism-related conditions (18% and 11%, respectively) compared with married (3%) and widowed (6%) patients. The adjusted OR for pneumonia-related hospitalization was increased, at 1.29 (95% confidence interval [CI]: 1.25–1.33) among divorced; 1.15 (95% CI: 1.12–1.17) among widowed; and 1.33 (95% CI: 1.29–1.37) among never-married individuals as compared with those who were married. Conclusion Married individuals have a decreased risk of being hospitalized with pneumonia compared with never-married, divorced, and widowed patients.