question: Purpose: Coronavirus disease 2019 (COVID-19) pandemic has spread worldwide rapidly and patients with cancer have been considered as a vulnerable group for this infection. This study aimed to examine the expressions of angiotensin-converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSS2) in tumor tissues of six common cancer types. Materials and Methods: The expression levels of ACE2 and TMPRSS2 in tumors and control samples were obtained from online databases. Survival prognosis and biological functions of these genes were investigated for each tumor type. Results: There was the overexpression of ACE2 in colon and stomach adenocarcinomas compared to controls, meanwhile colon and prostate adenocarcinomas showed a significantly higher expression of TMPRSS2. Additionally, survival prognosis analysis has demonstrated that upregulation of ACE2 in liver hepatocellular carcinoma was associated with higher overall survival (hazard ratio=0.65, p=0.016) and disease-free survival (hazard ratio=0.66, p=0.007), while overexpression of TMPRSS2 was associated with a 26% reduced risk of death in lung adenocarcinoma (p=0.047) but 50% increased risk of death in breast invasive carcinoma (p=0.015). Conclusion: There is a need to take extra precautions for COVID-19 in patients with colorectal cancer, stomach cancer, and lung cancer. Further information on other types of cancer at different stages should be investigated.