We have performed a magnetoreflectivity study of excitons in epilayers of the diluted magnetic semiconductor Zn1−xFexSe. The samples were grown by molecular‐beam epitaxy on GaAs (100) substrates to a typical thickness of 1 μm. Using both Faraday and Voigt geometries and magnetic spin splittings of the conduction and valence bands. The band splitting was found to be linear in magnetic field B and B<6 T. We measure effective g factors of 33.4 and 28.3 for the conduction and valence bands, respectively. For fields B>6 T, deviations were observed. The band spin splitting was also studied as a function of temperature at constant fields. At low temperatures, the spin splitting is independent of temperature. These data are in agreement with previous magnetization studies1 which showed that ZnFeSe, unlike Mn‐based diluted magnetic semiconductors, exhibits Van Vleck paramagnetism. The temperature study of the band splitting allowed a determination of the crystal field splitting. © 1988, American Institute of Physics. All rights reserved.