Abstract Aim . To estimate the fraction of hospitalizations and deaths from COVID-19 attributable to chronic diseases due to poor nutrition and smoking in Mexico . Methods . We used data from the Mexican surveillance system of COVID-19 . We considered six chronic diseases (obesity, COPD, hypertension, diabetes, cardiovascular disease, and chronic kidney disease) to define a multimorbidity variable: no diseases , 1 disease , 2 diseases, or 3 or more diseases . We calibrated the database using bias quantification methods to consider the undiagnosed cases of chronic diseases . To estimate the risks of hospitalization and death due to chronic diseases, we fitted Poisson regression models with robust standard errors, adjusting for possible confounders . Using these risks, we calculated attributable fractions using the population attributable fraction (PAF). Results . Chronic diseases accounted for to 25.4% (24.8% , 26.1 %), 28.3% (27.8% , 28.7 %) and 15.3% (14.9% ,15.7 %) of the hospitalizations among adults below 40 years , 40 to 59, and 60 years and older respectively (95% CI). For COVID-19-related deaths , 50.1% (48.6% , 51.5 %), 40.5% (39.7% , 41.3 %), and 18.7% (18.0% , 19.5 %) were attributable to chronic diseases in adults under 40 years , 40 to 59, and 60 years and older, respectively . Conclusion . Chronic diseases linked to malnutrition and tobacco use contributed to a higher burden of hospitalization and deaths from COVID-19 in Mexico, particularly among younger adults . Medical and structural interventions to curb chronic disease incidence and facilitate disease control are urgently needed.