Neutron irradiation induced degradation in the responsivity of Si and Ge p-i-n photodetectors has been studied. The responsivity of an irradiated photodetector normalized to its preirradiation responsivity was found to have a spectral dependence in the case of the Si photodetector. In the case of the Ge photodetector, the relative responsivity was found to be independent of wavelength in the most part of the spectrum covered in the experiment.