Object: To investigate the association between Kaposi’s sarcoma-associated herpesvirus (KSHV)/human herpesvirus 8 (HHV8) infection and both all-cause and cardiovascular mortality in a representative cohort of US adults. Methods: Data from the National Health and Nutrition Examination Survey III (NHANES III; 1988-1994) were analyzed, including 13,993 participants aged 18-90 years who underwent KSHV serology evaluations. Mortality outcomes were ascertained through December 2019 using the National Death Index. Cox proportional hazards models were employed to examine the association between KSHV seropositivity and mortality, adjusting for potential confounders such as age, sex, ethnicity, body mass index, and smoking status. Results: Over a median follow-up period of 26.5 years, 5,503 deaths were recorded. KSHV seropositivity was associated with an increased hazard of all-cause mortality (Hazard Ratio [HR]: 1.32, 95% Confidence Interval [CI]: 1.03-1.69) and cardiovascular mortality (HR: 1.58, 95% CI: 1.00-2.50) after adjusting for age, sex, ethnicity, and body mass index. However, further adjustment for smoking status attenuated these associations. Notably, the association between KSHV infection and all-cause mortality persisted among women (HR: 1.32, 95% CI: 1.02-1.72) after adjusting for all confounders, whereas the association with cardiovascular mortality was only statistically significant for men (HR: 1.90, 95% CI: 1.02, 3.53). Conclusions: KSHV infection may represent an independent risk factor for all-cause and cardiovascular mortality among US adults. These findings highlight the need for further research to validate these associations in independent populations and to elucidate the biological mechanisms underlying the observed increased mortality associated with KSHV infection.