Iron sulfide nanomaterials were prepared by the solvothermal decomposition of two single source precursors i.e. [FeCl2(cinnamtscz)2] (1) (cinnamtscz = cinnamaldehyde thiosemicarbazone) and [FeCl2(benztscz)2] (2) (benztscz = benzaldehyde thiosemicarbazone) at different temperatures of 230 and 300 °C in the presence of oleylamine. Powder X-ray diffractometry shows the formation of the pyrrhotite phase at both reaction temperatures. The solvothermal decomposition of [FeCl2(cinnamtscz)2] and [FeCl2(benztscz)2] at 230 °C produced iron sulfide nanoparticles in the form of spheres. When the temperature was increased to 300 °C, particles in the form of hexagons and nanorods were obtained. Furthermore, the photocatalytic activities of all the four iron sulfide nanomaterials were tested for the degradation of methylene blue under visible light irradiation. Amongst all the materials, nanospheres of iron sulfide obtained by the solvothermal decomposition of [FeCl2(benztscz)2] at 230 °C showed the highest photocatalytic efficiency (88.40%).National Research Foundation (NRF), South Africa and the India–Brazil–South Africa (IBSA) program