The present work is based on the development and application of a photoelectrochemical method for the amperometric determination of 3,4,5-trihydroxybenzoic acid in different samples. The method is based on the use of a photoelectrochemical platform based on a glass slide coated with fluorine-doped tin oxide, which has been modified with cadmium sulfide and poly(D-glucosamine) and subjected to a light-emitting diode (LED) lamp. The photoelectrochemical platform was sensitive to the increase of the concentration of the antioxidant 3,4,5-trihydroxybenzoic acid in the solution. Under the optimized experimental conditions, the photoelectrochemical method presented a linear response for a 3,4,5-trihydroxybenzoic acid concentration ranging from 0.2 up to 500 μmol L-1. The method was applied to 3,4,5-trihydroxybenzoic acid determination in samples of wines and teas with recoveries between 95.88 and 101.72%. The results obtained suggest that the developed platform is a promising tool for quantifying the 3,4,5-trihydroxybenzoic acid.