The design and construction of high-performance photoelectrode with efficient visible-light absorption and fast charge transport rate are crucial to developing photoelectrochemical (PEC) sensor. Herein, a well-aligned amorphous MoSx (a-MoSx)@ZnO core-shell nanorod arrays was uniformly grown on indium tin oxide (ITO) via a facile all-electrochemical strategy. Simultaneous boosted PEC performance and stability in the visible region were obtained. Those could be attributed to the collaboration effect of fast electron transfer path within the oriented ZnO nanorod and extended visible-light absorption upon combining a-MoSx, as well as favorable energy-band alignment between the two PEC materials. By employing tobramycin-binding aptamer as recognition element, a self-powered PEC aptasensor for tobramycin was successfully fabricated for the first time. The sensor exhibited a rapid response in a wide linear range of 0.010-50 ng/mL with good stability and reproducibility. The detection limit was as low as 5.7 pg/mL. Ultrasensitive and high-affinitive determination of tobramycin in serum samples was realized at 0 V (vs.SCE) with desired accuracy and satisfactory recovery. This work reveals the promising application of all-electrodeposited a-MoSx@ZnO NR arrays-based photoanode for self-powered PEC bioassay in the tobramycin-related disease diagnosis.