Controversial data exist regarding the impact of body mass index (BMI) on TAVI outcomes. Thirteen TAVI studies were included and analyzed for the incidence of procedural complications, 30-day, and long-term all-cause mortality. Three comparisons were executed: (1) underweight versus normal weight, (2) overweight versus normal weight, and (3) obese versus normal weight patients. Underweight patients (BMI <20 kg/m²) had similar 30-day all-cause mortality compared with the normal, although they displayed a significant worse survival at long-term follow-up (hazard ratio 1.68, 95% confidence interval (CI) 1.09 to 2.59, p = 0.02). Underweight patients showed a higher incidence of major and life-threatening bleedings (2,566 patients, odds ratio 1.64, 95% CI 1.10 to 2.45, p = 0.02) and of major vascular complications (2,566 patients, odds ratio 1.86, 95% CI 1.16 to 2.98, p = 0.01), compared with normal weight patients. Overweight patients (BMI ≥25 and <30 kg/m²) display similar 30-day and long-term all-cause mortality, as well as similar procedural complication rate compared with normal weight patients. Obese patients (BMI >30 kg/m²) had similar 30-day all-cause mortality rates compared with the normal weight category, whereas they displayed a significant better survival at long-term (hazard ratio 0.79, 95% CI 0.67 to 0.93, p = 0.004). Procedural complications did not differ between obese and normal body weight patients. In conclusion, a low BMI is linked to a significantly worse prognosis after TAVI. Therefore, BMI represents an important and handily tool that might be used in the risk prediction of patients to be addressed for TAVI.