Silver nanoparticles (AgNPs) have been frequently studied in the scientific field due to their physical, chemical and biological properties. These characteristics are influenced by the nanomaterials' size, morphology and composition , allowing the application of AgNPs in the biomedical area due to their antimicrobial action. This work studied the influence of sodium citr ate concentration on the size of silver nanoparticles. Characterization techniques such as DLS and UV visible spectr oscopy were applied to analyze nanoparticle stability, size and polydispersity index. Characterization was carried out using a UV Vis Spectrophotometer and TEM (Transmission Electron Microscope). Analysis of the UV Vis spectra shows that the relatively sta ble nanoparticles at the maximum wavelength measurement of 417 to 418 nm are synthesized using 35, 55 and 100 mmol/L of sodium citrate. Characterization using TEM and XRD analysis shows that silver nanoparticles synthesized based on sodium citrate concentr ation have the smallest size in the 15.5 34.56 nm range with a face centred cubic (FCC) crystal structure. The nanoparticles utilized in this study demonstrated greater antimicrobial activity against Gram positive bacteria than Gram negative bacteria.