Nucleic acid and antibody detection assays have been utilized in COVID-19 laboratory diagnosis. However, the use of viral antigenic proteins for diagnosis has not been successfully developed. Using viral antigen allows rapid direct viral detection earlier than production of antibodies. The present study was aimed at evaluating the performance of two COVID-19 rapid antigen detection tests, which are BIOCREDIT COVID-19 Ag (RapiGEN Inc., Korea) and Standard Q COVID-19 Ag (SD Biosensor, Korea), in comparison with RT-PCR. These tests were performed on 80 COVID-19 RT-PCR positive respiratory samples and 20 RT-PCR negative control samples. BIOCREDIT COVID-19 Ag and SD Biosensor RAD kits recorded total sensitivities of 52.5% and 68.7% and specificities of 46% and 96%, respectively. In high viral load samples, BIOCREDIT COVID-19 Ag and SD Biosensor RAD kits recorded higher sensitivities of 60% and 77%, compared to 45% and 60% in normal viral load samples, respectively. Sensitivity and specificity of the 2 antigen kits varied significantly with P values of <0.000001 and 0.0135, respectively. The evaluated RAD tests presented promising performance which was relatively better for SD-Biosensor than BIOCREDIT RAD tests, especially in high viral load samples. However, antigen tests are still considered substandard in comparison with RT-PCR in detecting SARS-CoV-2.