In this work, the optoelectronic properties of Be-doped CdO films grown on p-Si forming CdO : Be/p-Si hetero-p-n junctions were investigated. The spotlight was on the influence of electronic properties of CdO : Be layers, which were controlled by Be-dopant content, on the optoelectronic properties of the constructed p-n heterojunction. The characterization of the transparent conducting oxide CdO : Be layer was performed with X-ray diffraction, scanning electron microscopy, electrical measurements and spectral photometry. It was found that Be doping greatly enhanced the optoresponse (S*) of the p-n heterojunction, such that S* was boosted by ~36 times for CdO : 0⋅10% Be/p-Si sample, compared with the undoped CdO/p-Si. This S*-enhancement was explained by the improvement of carrier mobility in host CdO with Be doping. Therefore, the utmost S* that was found with 0⋅10% Be-doped CdO sample was due to its highest carrier mobility among other samples of different Be content. The results of optoelectronic measurements in visible and NIR spectral range demonstrate the utility of the CdO : Be/p-Si heterojunction in photodetection applications.