Background Heterogeneous evidence exists on the effect of coronavirus disease 2019 (COVID‐19) on the clinical outcomes of patients with cancer. Methods A systematic review was performed using the Medline, Embase, and CENTRAL databases and the World Health Organization Novel Coronavirus website to identify studies that reported mortality and characteristics of patients with cancer who were diagnosed with COVID‐19. The primary study outcome was mortality, defined as all‐cause mortality or in‐hospital mortality within 30 days of initial COVID‐19 diagnosis. The pooled proportion of mortality was estimated using a random‐effects model, and study‐level moderators of heterogeneity were assessed through subgroup analysis and metaregression. Results Among 2922 patients from 13 primarily inpatient studies of individuals with COVID‐19 and cancer, the pooled 30‐day mortality rate was 30% (95% CI, 25%‐35%). The overall pooled 30‐day mortality rate among 624 patients from 5 studies that included a mixture of inpatient and outpatient populations was 15% (95% CI, 9%‐22%). Among the hospitalized studies, the heterogeneity (I 2 statistic) of the meta‐analysis remained high (I 2 , 82%). Cancer subtype (hematologic vs solid), older age, male sex, and recent active cancer therapy each partially explained the heterogeneity of mortality reporting. In multivariable metaregression, male sex, along with an interaction between the median patient age and recent active cancer therapy, explained most of the between‐study heterogeneity (R 2 , 96%). Conclusions Pooled mortality estimates for hospitalized patients with cancer and COVID‐19 remain high at 30%, with significant heterogeneity across studies. Dedicated community‐based studies are needed in the future to help assess overall COVID‐19 mortality among the broader population of patients with cancer.