Interestingly, a structural transformation of zinc blende CdS nanoparticles into hexagonal wurtzite nanoparticles was observed during the formation of ferrite nanoparticles loaded onto the CdS heterojunction system. The interplanar spacing of 0.33 and 0.31 nm in the nanocomposites corresponds to the (002) and (101) planes of wurtzite CdS, providing direct proof of the conversion. On the other hand, the interplanar spacings of 0.29 and 0.25 nm could be indexed to the (220) and (311) planes of ferrite nanoparticles, revealing the successful decoration of ferrite nanoparticles over the CdS nanoparticles and nanorods. The band gap energy values of the CdS nanoparticles and nanorods decreased when they were decorated with the ferrite nanoparticles. The synthesized heterojunction showed enhanced photocatalytic performance for the mitigation of organic pollutants, without the need for an oxidant, when compared to both CdS and ferrite nanoparticles. This work not only enriches our knowledge of heterojunction formation, but also reveals that the combined effect of structural transformation and charge separation in the nanocomposites induced by the synergistic effect of CdS and ferrites could bring enhanced photocatalytic activity, suggesting the tremendous potential of these nanocomposites for water purification at an industrial level.