This umbrella review examines the impact of plant-based diets (PBDs) on the risk factors associated with cardiometabolic diseases and cancer, as well as their related mortalities. The review includes systematic reviews and meta-analyses published from January 1, 2000, to June 31, 2023, focusing on human subjects of all ages. The study found that vegetarian and vegan diets are significantly associated with better lipid profiles, glycemic control, body weight/BMI, and lower inflammation levels. Vegetarian diets are also linked to lower mortality from cardiovascular diseases (CVDs). However, no significant differences were observed in the risk of gestational diabetes and hypertension in pregnant women following vegetarian diets. The quality of the included studies was generally average, with a high degree of heterogeneity in sample size, demographic features, geographical origin, dietary patterns, and other lifestyle confounders. The review concludes that PBDs appear beneficial in reducing cardiometabolic risk factors and cancer risk and mortality, but caution is advised due to the methodological limitations and potential risks associated with restrictive dietary regimens.This umbrella review examines the impact of plant-based diets (PBDs) on the risk factors associated with cardiometabolic diseases and cancer, as well as their related mortalities. The review includes systematic reviews and meta-analyses published from January 1, 2000, to June 31, 2023, focusing on human subjects of all ages. The study found that vegetarian and vegan diets are significantly associated with better lipid profiles, glycemic control, body weight/BMI, and lower inflammation levels. Vegetarian diets are also linked to lower mortality from cardiovascular diseases (CVDs). However, no significant differences were observed in the risk of gestational diabetes and hypertension in pregnant women following vegetarian diets. The quality of the included studies was generally average, with a high degree of heterogeneity in sample size, demographic features, geographical origin, dietary patterns, and other lifestyle confounders. The review concludes that PBDs appear beneficial in reducing cardiometabolic risk factors and cancer risk and mortality, but caution is advised due to the methodological limitations and potential risks associated with restrictive dietary regimens.