In 2019, a novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is transmitted via airborne route, caused a new pandemic namely, “coronavirus disease 2019” (COVID-19). Although it is still debated whether the use of masks can prevent the transmission of SARS-CoV-2, no study has evaluated the virus-blocking efficacy of masks used by patients. We aimed to evaluate this efficacy of masks used by SARS-CoV 2-infected individuals. Data, masks used, and nasopharyngeal swab samples were obtained from these patients. Forty-five paired samples of nasopharyngeal swabs and masks were obtained and processed; the majority of masks were woven. Viral RNAs were amplified using quantitative reverse‐transcription polymerase chain reaction and detected only on the inner parts of masks. Median cycle threshold (Ct) values of swabs and masks were 28.41 and 37.95, respectively. Statistically, there was a difference of approximately 10 Ct values between swabs and masks and no significant difference in Ct values among different types of masks. There were statistically significant differences in Ct values between men and women and symptomatic and asymptomatic patients. Our findings suggest the blocking of the transmission of viruses by different types of masks and reinforce the use of masks by both infected and non-infected individuals.