Synthesis of Ag/CaCO3 nanocomposites was accomplished by a two step technique. CaCO3 nanoparticles were synthesized by ultrasound assisted precipitation technique followed by deposition of silver via bio-inspired technique using a bio-reductant obtained from Andrographis panicolom and Aloe vera. X-ray diffraction pattern has confirmed the formation of CaCO3 with Calcite phase along with few minor peaks of Vaterite and Ag with face-centered cubic structure. Electron microscopy analysis has indicated the deposition of Ag nanopaticles on CaCO3. Resulting material was studied as catalyst for the reduction of 4-nitrophenol. The efficiency of the nanocomposites was found to be 10 fold higher than that of Ag nanoparticles and remained nearly unaltered for three consecutive cycles. Developed material is expected to be a potential catalyst candidate for environmental applications.