Epidemiologic evidence on the association between dietary choline and betaine and mortality risk remains limited, particularly among non-Western populations. We examined the association of dietary choline and betaine with all-cause mortality in Chinese adults using data from the China Health and Nutrition Survey (CHNS) 1991-2015. We included 9,027 men and 8,828 women without cardiovascular disease and cancer at baseline. Dietary intake was assessed using 3-day 24-hour dietary recalls in combination with a household food inventories. Death was ascertained through household surveys in each wave. We used time-dependent Cox proportional hazards regression models to estimate multivariable-adjusted hazard ratios (HRs) and 95% confidence intervals (CIs). During a median follow-up of 9.1 years, 891 men and 687 women were deceased. Higher total choline intake was associated with a lower risk of all-cause mortality in both men [HRQ5 vs. Q1 = 0.58 (95% CI: 0.45, 0.74)] and women [HRQ5 vs. Q1 = 0.59 (95% CI: 0.44, 0.78)]. The dose-response curve followed a reverse J-shape in men and an L-shape in women (both P-nonlinear ≤ 0.005). Similarly, fat-soluble choline intake was inversely associated with the risk of all-cause mortality in both men [HRQ5 vs. Q1 = 0.59 (95% CI: 0.46, 0.75)] and women [HRQ5 vs. Q1 = 0.53 (95% CI: 0.40, 0.70)], showing reverse J-shaped patterns (both P-nonlinear < 0.001). A J-shaped association between dietary water-soluble choline and all-cause mortality was observed in women (P-nonlinear < 0.001), but a null association was found in men. Betaine intake was not associated with all-cause mortality in either sex. Our findings suggest that adequate choline intake, but not betaine, is linked to reduced all-cause mortality in Chinese adults with predominantly plant-based diets, with both insufficient and excessive choline intake potentially increasing mortality risk.