Background: High body-mass index (BMI) is a major contributor to the global burden of cardiometabolic diseases (CMD) like type 2 diabetes mellitus (T2DM) and cardiovascular diseases (CVD). We aimed to quantify the mortality burden associated with high BMI in Peru to inform policies and set priorities. Methods: We computed population attributable fractions (PAF) combining BMI prevalence estimates from the Peruvian Demographic and Health Survey and relative risks between high BMI and CMD mortality from the GBD 2019 Study. PAFs were multiplied by the CMD deaths recorded in the national death registry to obtain the absolute number of CMD deaths attributable to high BMI in each region, sex and five-year age group. Results: In 2018, the absolute number of T2DM deaths attributable to high BMI in Peru was 1,376 (50.3%) in men and 1,663 (56.0%) in women; the absolute number of CVD deaths related to high BMI was 1,665 in men (23.6%) and 1,551 (24.7%) in women. Most CMD deaths related to high BMI were attributable to obesity class 1 and overweight. Regions with the highest proportions of CMD deaths related to high BMI were in the Amazon (Madre de Dios, Ucayali) and the Coast (Tacna, Moquegua); conversely, regions with the lowest proportions were in the Highlands (Huancavelica, Apurimac). Conclusions: High BMI is a major contributor to the CMD mortality burden in Peru, with high variability across regions. Health policies need to be strengthened to reduce BMI at the population level, which may have a subsequent reduction in the associated CMD mortality.