In this work, nanoparticles of Fe3O4 and CoWO4 were decorated over graphitic carbon nitride (g-C3N4) to fabricate very efficient visible-light-responsive photocatalysts through a facile refluxing-calcination method. Among the fabricated photocatalysts, the g-C3N4/Fe3O4/CoWO4 (10%) nanocomposite displayed superior activity in degradation of RhB, which is 12.5 and 11.5 times superior than the pristine g-C3N4 and g-C3N4/Fe3O4 photocatalysts, respectively. Additionally, exceptional performance of the ternary photocatalyst was confirmed in degradations of three organic pollutants under visible light. Higher harvesting ability of visible light and effective separation of electron/hole pairs from recombination are two main factors responsible for the observed exceptional photocatalytic activity of the ternary nanocomposite. Due to enough saturation magnetization of the ternary nanocomposite, the photocatalyst was entirely separated from the degradation system by a conventional magnet. Finally, photostability of the ternary photocatalyst during four successive runs was confirmed.