The novel Bi2MoO6-Ag2MoO4 nano-photocatalyst was prepared via facile sono-chemical route. Bi2MoO6-Ag2MoO4 nanocomposite was characterized by high-resolution transmission electron microscopy (HR-TEM), fourier transverse infrared spectroscopy (FTIR), X-ray diffraction (XRD), BET surface area analyzer, photoluminescence (PL), X-ray photoelectron spectroscopy and UV–visible diffuse reflectance spectroscopy. XRD and SAED pattern shows that the particles were crystalline in nature. The formation of heterojunction with tuned band gap of 2.89 eV enhanced the photocatalytic performance of nanocomposite under visible light irradiation. Bi2MoO6-Ag2MoO4 nanocomposite followed the pseudo-first order kinetic and it showed high correlation coefficient value (R2 > 0.95), and it fitted well to the Langmuir–Hinshelwood model. Bi2MoO6-Ag2MoO4 nanocomposite exhibited 91.8% degradation which was highly effective than individual Ag2MoO4 (54.66%) and Bi2MoO6 (58.6%). The radical trapping study reveals the key reactive species involved in photocatalytic degradation process such as .OH. The Bi2MoO6-Ag2MoO4 nanocomposite was found to be highly reusable for the degradation of MB dye by showing 91.8% degradation efficiency after 6th cycle. Antimicrobial activity of the Bi2MoO6-Ag2MoO4 nanocomposite was superior when compared with Ag2MoO4 and Bi2MoO6 nanoparticles. The prepared nanocomposite proved a robust alternative as a solar radiation driven photocatalyst and it also acts as an antimicrobial agent for the treatment of environmental water.