Background and Objectives: Previous prospective studies have reported inconsistent findings on the association between obesity and mortality in patients with COVID-19. This study aimed to investigate the association between them by using a meta-analysis of prospective studies. Methods and Study Design: We searched PubMed and EMBASE to retrieve studies using keywords related to this topic on January 3, 2022. Data were extracted for a random-effects meta-analysis to calculate a pooled odds ratio (OR), relative risk (RR), or hazard ratio (HR) with a 95% confidence interval (CI). Results: In the meta-analysis of 15 prospective cohort studies, obesity significantly increased the risk of mortality in patients with COVID-19 (OR/RR/HR, 1.52; 95% CI, 1.26 to 1.84; I^2 = 90.4%). Most of the included studies were conducted in European (n = 10) and North American (n = 4) countries. In the subgroup meta-analysis by continent, there was a significant association between them in European countries (OR/RR/HR, 1.78; 95% CI, 1.30 to 2.43; I^2 = 81.4%). Also, in the subgroup meta-analysis by data source, obesity was significantly associated with the increased mortality in patients with COVID-19 in both population-and hospital-based data. Conclusions: We found that obesity is associated with the increased risk of mortality in patients of COVID-19.