In the present work, silver nanoparticles were synthesized using an easy, simple, and environment-friendly method based on principles of green chemistry in the absence of a sophisticated laboratory, and their anti-cancer properties were studied. Silver nanoparticles were synthesized using electrolytic deposition. As-synthesized nanoparticles were capped using black tea leaf extract. MTT assay was used to investigate anti-cancer activity. X-ray diffraction graphs show highly pure as-synthesized silver nanoparticles. Transmission electron microscopy images show well-dispersed spherical nanoparticles, with an average size of 9 and 15 nm, corresponding to different values of parameters used in the synthesis. For the MCF-7 cancer cell lines, 100% growth inhibition is obtained. The 50% growth inhibition concentration values against MCF-7 cancer cell lines were obtained at 70- and 30-fold dilutions of colloidal silver of almost the same concentration, 178 μg/ml, for both configurations. Silver nanoparticles can be synthesized, and their morphology can be tuned using the electrolytic deposition method with black tea leaf extract as capping agent. Silver nanoparticles with an average size of 9 nm are more effective those with an average size of 15 nm. The synthesis method is faster, cheaper, and environment friendly and renders a treatment option that can have high accessibility, reduced harmful side effects, and increased economic benefits.