In the present study, silver (AgNPs) and gold (AuNPs) nanoparticles have been prepared using ethanolic extract of Nepeta leucophylla (NLe). This plant was considered owing to its richness in natural polyphenols and antioxidants that are well known for their reducing potential. Different techniques such as UV (Ultraviolet-visible spectrophotometer), FTIR (Fourier transform infrared), XRD (X-ray diffraction) were utilized for the characterization of nanoparticles. The UV absorption peak was observed at 434 nm and 535 nm for NLe-AgNPs and NLe-AuNPs respectively. FTIR suggested about the possible classes of biomolecules involved in the formation of metal nanoparticles. XRD pattern confirmed the crystalline structure of gold and silver nanoparticles and validated that the crystal structure under consideration is a face-centered cubic (FCC) pattern. HR-TEM images revealed that the NLe-AgNPs and NLe-AuNPs nanoparticles were spherical in shape, with average diameters of 11.4 nm and 7.8 nm respectively. The antioxidant potential was assessed using the DPPH assay, which revealed that NLe exhibited the highest antioxidant potential (79.37 %) compared to synthesized metal nanoparticles. Further, cytotoxic potential was evaluated using MTT assay against Hep G2 cell lines. The IC50 values were determined to be 5.97 µg/mL for NLe, 12.31 µg/mL for NLe-AgNPs, and 34.58 µg/mL for NLe-AuNPs.