In recent years, biosynthesized silver nanoparticles (AgNPs) attained great interest due to their eco-friendly, cost-effective, and biocompatible nature. Silver nanoparticles (Ag-NPs) were synthesized with leaves extract of Naringi crenulata (NC-AgNP), where Ag + was converted to Ag 0 . Phytochemicals such as alkaloids, flavonoids, phenols, and saponins were present in the Naringi crenulata and are considered to reduce silver. The synthesized NC-AgNP were significantly analyzed for its physiochemical characterization with UV–vis spectroscopy, XRD, FT-IR, particle size analyzer, Zeta-potential, Scanning Electron Microscopy (SEM). The synthesized NC-AgNP were in a size range of 20 nm to 40 nm, and the IC 50 value of NC-AgNPs was 72.88 μg/mL for HER2 + breast cancer cells. At this concentration, cellular functions of the cancer cell were affected, which was analyzed with the flow cytometric analysis. These analyses on the cell line of HER2 Positive Breast cancer (SK-BR-3) suggest that NC-AgNP would inhibit cell proliferation and deregulation of cell-cycle progression. Moreover, the phytochemicals of Naringi crenulata also reduces cell invasion of SKBR-3 cells. Compared to control (untreated), the NC-AgNPs prevented the proliferation of cancer cells. The research findings suggest that the NC-AgNPs act against breast cancer of HER2-positive through inactivation of HER2 and inducing apoptosis. These nanoparticles also could inhibit angiogenesis and metastasis in cancer cells. The results show the potential of silver nanoparticles synthesized from the leaf extracts of Naringi crenulata to be used as a treatment for breast cancer.