This study investigated the synthesis, characterization and in vitro antioxidant activity of silver nanoparticles (AgNPs) using the aqueous leaf extract of Justicia carnea.  The aqueous leaf extract of J. carnea was used as a potential reducing and capping agent. To identify the compounds responsible for the reduction of silver ions, the functional groups present in the plant extract were subjected to FTIR. The in vitro antioxidant activity of synthesized nanoparticles was evaluated in terms of ferric reducing antioxidant potential (FRAP), DPPH (1,1-diphenyl-2-picrylhydrazyl) and ABTS (2,2`-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) free radicals scavenging assays. The surface plasmon resonance confirmed the formation of AgNPs with maximum absorbance at kmax = 446 nm. FTIR revealed the biological macromolecules of J. carnea leaf extract involved in the synthesis and stabilization of AgNPs. UV-Visible spectrophotometer showed absorbance peak in the range of 436-446 nm. The silver nanoparticles exhibited moderate antioxidant activities compared to standard antioxidants (ascorbic acid and BHT). These results confirmed this protocol as simple, eco-friendly, nontoxic and an alternative for conventional physical and chemical methods. It can be concluded that J. carnea leaf extract can be used effectively in the production of potential antioxidant AgNPs which could be useful in various bio-applications such as cosmetics, food and biomedical industry.