Abstract Background The link between oral diseases and mortality remains under-explored. We aimed to evaluate the associations between tooth count, untreated caries and risk of all-cause and cause-specific mortality. Methods Data on 24 029 adults from the National Health and Nutrition Examination Survey 1988–94/1999–2010, with mortality linkage to the National Death Index to 31 December 2015, were analysed. Baseline total number of permanent teeth and any untreated caries were assessed by trained dental professionals. Results During up to 27 years of follow-up, 5270 deaths occurred. Fewer permanent teeth were associated with higher all-cause mortality, including heart disease and cancer mortality (all P <0.05 for trend) but not cerebrovascular disease mortality. For every 10 teeth missing, the multivariable-adjusted hazard ratios (HRs) were 1.13 (95% CI: 1.08 to 1.18) for all-cause, 1.16 (95% CI: 1.05, 1.29) for heart disease and 1.19 (95% CI: 1.09, 1.29) for cancer mortality. Untreated caries was associated with increased all-cause (HR: 1.26, 95% CI: 1.15, 1.39) and heart disease mortality (HR: 1.48, 95% CI: 1.17, 1.88) but not cerebrovascular disease/cancer mortality, after adjusting for tooth count, periodontitis and sociodemographic/lifestyle factors. Compared with those without untreated caries and with 25–28 teeth, individuals with untreated caries and 1–16 teeth had a 53% increased risk of all-cause mortality (HR: 1.53, 95% CI: 1.27, 1.85) and 96 % increased risk of heart disease mortality (HR: 1.96, 95% CI: 1.28, 3.01). Conclusions In nationally representative cohorts, fewer permanent teeth and untreated caries were associated with all-cause and heart disease mortality. Fewer teeth were also associated with higher cancer mortality.