A visible-light driven photoelectrochemical (PEC) aptasensor is described that is capable of detecting chloramphenicol (CAP). It is based on the use of a TiO based nanorod array (NRA) sensitized with Eu(III)-doped CdS quantum dots. The NRA absorbs visible-light and while strongly depressing the recombination of photogenerated charges, thereby improving photo-to-current conversion efficiency. The introduction of Eu(III) ions promotes the charge transformation and utilization, and this results in a further increase of photocurrent. The NRA was employed as the photoactive material for the fabrication of a PEC aptasensor. CAP-binding aptamers were immobilized on a fluorine-doped tin oxide (FTO) electrode that was modified with the NRA. The aptasensor was applied to the determination of CAP by monitoring the decrease in photocurrent (at a typical voltage of 0 V) that is caused by the formation of the aptamer-CAP complex. Under optimal conditions, the response is linear in the 1.0 pM to 3.0 nM CAP concentration range, with a detection limit of 0.36 pM (at S/N = 3). The method was applied to the determination of CAP in spiked milk samples where it gave satisfactory results. Graphical abstract Schematic presentation of the fabrication of a visible-light driven photoelectrochemical aptasensor based on the use of a TiO nanorod array sensitized with Eu(III)-doped CdS quantum dots. It was applied to the determination of chloramphenicol with good selectivity and high sensitivity. TiO NRA: TiO nanorod array; FTO: fluorine-doped tin oxide; CdS:Eu QDs: Eu(III)-doped CdS quantum dots; BSA: bovine serum albumin; CAP: chloramphenicol.