The COVID-19 pandemic persists without a definitive treatment, necessitating supportive therapies. Nirmatrelvir, an antiviral drug targeting the SARS-CoV-2 major protease (Mpro), has shown promise in inhibiting viral replication. Combined with ritonavir, it forms Paxlovid, recommended for high-risk COVID-19 patients. Accurate estimation of nirmatrelvir concentration is crucial for ensuring its efficacy and safety. High performance liquid chromatography (HPLC) is a reliable method for such analysis.