Theoretical investigation of crystal field parameters and zero-field splitting parameter of Fe3+ doped CdGa2Se4 single crystals is performed using superposition model and perturbation theory. The zero-field splitting parameter obtained agrees well with the experimental value determined from EPR. The theoretical investigation supports the experimental result that Fe3+ ions substitute at Ga3+ site in CdGa2Se4 single crystal. Using crystal field parameters and CFA program, the optical spectra of Fe3+ doped CdGa2Se4 crystal are computed. There is a reasonable agreement between the computed and experimental energy values. Thus our theoretical investigation supports the results of the experimental study.