This article reports the utilization of seed extract (GSE) from Gardenia jasminoides Ellis. in the synthesis of silver nanoparticles (Gs-AgNPs) with versatile biological activities. The synthesized Gs-AgNPs were spherical in shape, crystal lattice with an average size of 20 nm as confirmed by UV-vis spectrum, X-ray diffractometer (XRD), Transmission electron microscopy with Energy dispersive X-ray spectroscopy (TEM-EDS) and particle size analyses (PSA). Phenolic compounds, proteins, and terpenoids were likely involved in the Gs-AgNPs synthesis, as indicated by Fourier-transform infrared spectroscopy (FTIR) analysis. The minimum bactericidal concentration (MBC) of the Gs-AgNPs was 12.5 μg·ml-1 for S. enterica Typhimurium and 10 μg·ml-1 for S. aureus. The MBC of the Gs-AgNPs induced >70% bacterial cell death within 60 min, as confirmed by growth curve analysis followed by Confocal laser scanning microscope (CLSM). Gs-AgNPs showed the highest scavenging activity for 1, 2-diphenyl-1-picrylhydrazyl DPPH radical (92.3 ± 0.86%), Nitric oxide (NO) radical (72.5 ± 2.15%), and Hydrogen peroxide H2O2 radical (85.25 ± 1.45%). Anticancer results revealed an IC50 of 15.625 ± 1.3 μg·ml-1 for Gs-AgNPs, whereas it was 580.54 ± 2.5 μg·ml-1 for GSE. The Gs-AgNPs generated high reactive oxygen species (ROS) resulting in induced apoptosis as evident by up-regulation of apoptosis-related protein. In addition, the photocatalytic results revealed about 92% of the reduction in Coomassie Brilliant Blue dye color with Gs-AgNPs. Hence, this work provided economically viable and ecologically sustainable Gs-AgNPs as an alternative biomaterial for future therapeutic applications as antimicrobial, antioxidant, anti-cancer agents and in dye degradation for water remediation.