The aim of this study was to evaluate the diagnostic performance of the SARS-CoV-2 rapid antigen test (RAT) for the diagnosis of COVID-19 among symptomatic and asymptomatic patients. This retrospective study was done from 15th November 2021 to 15th December 2021, at National Medical Centre, Karachi, Pakistan. Two parallel nasopharyngeal swabs were collected from each patient, and SARS-CoV-2 RAT and SARS-CoV-2 real-time polymerase chain reaction (RT-PCR) were done. A total of 719 patients were included, mean age was 46.03+17.74 years with 378 (52.6%) males. The sensitivity was higher in symptomatic patients i.e. 95.18%, while RAT was found to be more specific in asymptomatic patients with a specificity of 99.83%. High diagnostic accuracy of 91.81% and 96.29% were noted in symptomatic and asymptomatic patients, respectively. SARS-CoV-2 RAT (Roche) can be used for early diagnosis of SARS-CoV-2 patients in busy emergency departments. Key Words: COVID-19, Diagnosis, Rapid antigen test, RT-PCR, Emergency service.