Heterostructured ternary nanocomposites of silver doped magnetites with ZnO (Z), namely Ag/ZnO (AZ), Ag/Fe3O4 (AF), ZnO/Fe3O4 (ZF) and Ag/ZnO/Fe3O4 (AZF) were synthesized. X-ray diffraction studies indicated the formation of wurtzite hexagonal phase for ZnO, cubic structure for Fe3O4 and FCC structure for silver nanocomposites. Field emission scanning electron microscopy revealed the uniform distribution of granules of AZF. Fourier transform infrared spectroscopic studies confirmed the presence of M–O bonds. The ultra violet-visible diffuse reflectance spectroscopy and photoluminescence studies indicated the higher photo degradation activity of silver doped nanocomposites. Thermogravimetric analysis point towards the enhanced thermal stability of doped and coupled nanocomposites. Hydrogenation of 4-nitrophenol to 4-aminophenol showed that AZ, AF & AZF completed the reaction within 3, 4 & 2 min respectively while Z and ZF are ineffective. The photo catalytic activity of the nano composites was investigated by studying the degradation of malachite green (MG) & methylene blue (MB) under UV irradiation. Hetero structured and Ag doped nano composites exhibited better degradation efficiency of MG & MB. Using well diffusion method antibacterial activity of the as-prepared nanoparticles was tested against gram-positive bacteria Staphylococus aureus and gram negative bacteria Escherichia coli. AF & AZF nanocomposites exhibited strong antibacterial activity with greater inhibition zones due to the synergistic effect of silver and magnetite nanoparticles.