There are minimal data regarding the prevalence of cancer in patients with coronavirus disease 2019 (COVID-19), as well as the incidence of severe illness and rate of mortality in COVID-19 patients with cancer. PubMed, Embase, Cochrane Library, and Web of Science were systematically searched, from database inception to July 15, 2020, for studies of patients with COVID-19 that included information regarding comorbid cancer. In total, 109 eligible global studies were included in this systematic review. Ninety studies with 94,845 COVID-19 patients, among which 4106 exhibited comorbid cancer, were included in the meta-analysis regarding prevalence of comorbid cancer. Twenty-three studies with 71,969 COVID-19 patients, among which 4351 with comorbid cancer had severe illness or death, were included in the meta-analysis. The overall prevalence of cancer among COVID-19 patients was 0.07 (95% CI 0.05–0.09). The cancer prevalence in COVID-19 patients was higher in Europe (0.22, 95% CI 0.17–0.28) than in the Asia-Pacific region (0.04, 95% CI 0.03–0.06) or North America (0.05, 95% CI 0.04–0.06). The cancer prevalence in COVID-19 patients aged >60 years was 0.10 (95% CI 0.07–0.14), while the prevalence among patients aged ≤60 years was 0.05 (95% CI 0.03–0.06). The pooled prevalence of severe illness among COVID-19 patients with cancer was 0.34 (95% CI 0.26–0.42) and the pooled mortality rate of COVID-19 patients with cancer was 0.20 (95% CI 0.16–0.25). Pooled incidences of severe illness among COVID-19 patients with cancer from Asia Pacific, Europe, and North America were 0.38 (95% CI 0.24–0.52), 0.39 (95% CI 0.25–0.53), and 0.26 (95% CI 0.20–0.31), respectively; pooled mortality rates from the Asia-Pacific region, Europe, and North America were 0.17 (95% CI 0.10–0.24), 0.26 (95% CI 0.18–0.35), and 0.19 (95% CI 0.13–0.25), respectively.