This study was carried out for the simple synthesis of zinc stannate (Zn2SnO4, ZTO): tin oxide (SnO2) nanocomposite photocatalyst in order to investigate the photodegradation of Rhodamine B (RhB) dye molecules under the UV light irradiation. For this purpose, nanocomposite photocatalysts were prepared via a low temperature hydrothermal method. Pure ZTO nanoparticles were also synthesized for the comparison purpose of the photocatalytic activity. Formation of the ZTO:SnO2 nanocomposites could be easily controlled by tuning of the hydrothermal reaction temperature. The structural properties of ZTO:SnO2 nanocomposites and ZTO nanoparticles were schematically characterized by XRD, XPS and FTIR. Morphological investigation was performed via SEM and TEM. Band structure and optical properties were investigated with UV–Vis spectroscopy and PL analyses. It was found that ZTO:SnO2 nanocomposites keep hexagonal ZTO nanoparticles and SnO2 nanorods together and have more surface defects than that of the ZTO nanoparticles. The degradation of RhB dye molecules in the presence of ZTO:SnO2 nanocomposites reached to 62.0% degradation after first 60 min and 94.5% after 240 min. The photocatalytic rate constant of the ZTO:SnO2 nanocomposites (k = 0.0111 min−1) was two times higher than that of the pure ZTO nanoparticles (k = 0.00527 min−1). In addition, ZTO:SnO2 nanocomposites exhibited very high stability in the cycling degradation test with 90.1% RhB degradation even after ten times cycling run.