Sorrel tree leaf extract reduced silver nanoparticles (AgNPs) in the lab. The extract's phytochemicals slowed and stabilised silver nanoparticles. Characterising nanoparticle size, shape, and morphology required many approaches. UV-visible, FT-IR, XRD, and SEM were used. All synthesised nanoparticles were spherical and monodisperse. FTIR spectrum stretching vibrations showed green extract stabilises silver nanoparticles. Further examination indicated that these small particles were Sorrel tree (ST) extract silver nanoparticles (ST-AgNPs). Biological synthesis improves silver nanoparticle effectiveness. By optimising these parameters, ST-AgNPs may combat lung cancer (A549 cell line) and breast cancer (MCF7 cell line) more effectively. A549 cells had a 49.52 g mL-1 IC50, whereas MCF7 cells had 78.40. The MTT experiment demonstrated that AgNP concentration correlated with cytotoxicity in both cell lines. Biosynthesized ST-AgNPs are highly anti-cancer. Spherical and monodispersed nanoparticles with significant cytotoxicity against cancer cells were synthesised using Sorrel tree leaf extract as a reducing agent.