Photo-electrochemical sensing is a new strategy for the development of clinical and environmental monitoring. Here, we present a new nanocomposite of cadmium sulfide decorated on cobalt oxide nano-dandelion (CoOx NDs/CdS NPs) aimed at glucose monitoring. Firstly, CoOx NDs are simply synthesized through hydrothermal technique; then, the resulted dandelion structures of CoO x are decorated with CdS nanoparticles through hydrothermal technique. The morphology of CoOx NDs/CdS NPs nanocomposite is characterized by transmission electron microscopy and scanning electron microscopy. The electrochemical properties and sensing ability is investigated by various voltammetric techniques. Beside of electrocatalytic activity, a remarkable photoelectrocatalytic activity toward oxidation of glucose under visible light irradiation is observed. Consequently, the limit of detection of the fabricated sensor toward glucose is 0.23 μM with a sensitivity of 0.46 μA/μM in the dark and 0.09 μM with 1.1 μA/μM under visible light irradiation, respectively. Furthermore, this sensor has displays respectable stability, fast response time, and interference tolerance. This proposed composite can be used in developing other photo-electrochemical sensors, bio anodes, and related biodevices.