Ertapenem is an antibiotic that is used in the treatment of several bacterial infections, and it was recently approved for the treatment of the COVID-19 virus. A simple validated stability-indicating reversed phase High Performance Liquid Chromatographic (RP-HPLC) method was developed for ertapenem estimation. The separation was done using Pronto SIL® C18 (300 × 4.6 mm, 5 μm) as the stationary phase, methanol, and acidified water as the mobile phase in gradient mode with a flow rate of 1 mL/min and a pH 4.0 adjusted by orthophosphoric acid. The method was validated according to ICH guidelines. The linearity ranges from 5.00-120.00 µg/mL with LOD 1.60 µg/mL and LOQ 4.85 µg/mL. Afterwards, the degradation behaviour of ertapenem was studied under various stress conditions, including acidic, basic, oxidative, thermal, and photolytic. The degradation study showed stability of ertapenem under thermal, photolytic degradation and severe degradation under acid, basic and oxidative conditions. The kinetics parameters were studied for acidic and basic degradation. The parameters showed that it follows a pseudo-first order reaction. Degradation products were structurally elucidated using mass spectrometry. The method has been evaluated as an excellent green analytical method based on eco-scale penalty points and the analytical greenness metric approach.