Silver nanoparticles (AgNPs) were biosynthesized using aqueous extract of Citrus japonica (Kumquat) and Candida tropicalis culture supernatant. AgNPs were characterized using FTIR, UV-Vis, TEM, XRD, DLS, and EDAX. XRD confirmed the crystalline nature with four characteristic peaks at 2Ɵ values corresponding to Ag-nanocrystals. TEM showed spherical-shaped AgNPs with average diameter of 4-20 nm. FTIR verified the presence of different bio-functional groups, such as, N-H, C-N, O-H, C-H, C-O-C, C=O, and C-NH₂ acting as stabilizing/reducing agents for AgNPs. The biosynthesized AgNPs exhibited excellent biocidal activity against some pathogenic Gram-positive, Gram-negative bacteria, and Yeast. MIC and MBC of biosynthesized AgNPs were determined using resazurin microtiter-plate assay. Biosynthesized AgNPs by C. tropicalis exhibited MBC of 12, 24,24, and 48 μg/mL against E. coli, Candida sp., K. pneumonia, and L. monocytogenes, respectively. The MBC of Kumquat-AgNPs were 48 μg/mL against (E. coli, K. pneumonia, Candida sp.), and 195 μg/mL against L. monocytogenes. SEM micrographs showed complete cell destruction of K. pneumonia and L. monocytogenes after 6hof treatment with MBC values. C. tropicalis-AgNPs exhibited better anticancer effect than Kumquat-AgNPs with IC₅₀ of 59.5 and 87.5 μg/mL, respectively, on Hep-G2cell lines. However, Kumquat-AgNPs proved less toxic than C. tropicalis-AgNPs towards normal cell lines with IC₅₀ values<300 and 69.9 μg/mL, on Human Skin Fibroblast, and 68.41 and 28.43 μg/mL, on Blood Lymphocytes, respectively. Detected IC₅₀were higher than the MBC values of biosynthesized AgNPs against studied pathogens, thus, could be recommended to apply the mas powerful antimicrobial bioagent.