Nanotechnology is an emerging multidisciplinary field that has the potential to offer solutions to pharmaceutical challenges starting from drug delivery to therapeutic applications. The plant-mediated method is eco-friendly and the most inexpensive of the various techniques used to synthesize nanoparticles (NPs). In this study, silver (Ag) NPs have been successfully synthesized using leaf extract of Catharanthus roseus and Ocimum tenuiflorum. X-ray diffraction revealed an average crystalline size of 19.96 and 21.42 nm for C. roseus and O. tenuiflorum-mediated Ag NPs, respectively. Further, shape, size, and elemental composition were analyzed using a scanning electron microscope, transmission electron microscope (TEM), and energy-dispersive X-ray spectral technique. TEM study revealed spherical/spheroidal-shaped Ag NPs were formed between 10−48 nm with C. roseus and 17−55 nm with O. tenuiflorum. Both synthesized Ag NPs inhibited Escherichia coli and Bacillus subtilis, where the effect was more prominent against E. coli (MIC 3.90 ± 0 µg/mL) with O. tenuiflorum Ag NPs. Mechanistic insights of antibacterial activity were also highlighted, and the activity might be attributed to the diverse mode of action of surface functionalized phytoconstituents and NPs.