The monitoring of pollutants such as sulfide anion species S2− and HS− is receiving a growing interest since they can cause acute and chronic toxicity including neurological effects and at high concentrations, even death. This study describes a new approach for optical detection of sulfide species in water samples. The method uses a silicon microchip with reagent-on-board and an integrated silicon photomultiplier (SiPM) device. The sulfide species are detected by the fluorescence signal emitted upon the reaction with N,N-dimethyl-phenylenediamine sulfate in the presence of iron(3+), leading to the formation of the fluorescent methylene blue (MB) species. A comparison with conventional fluorimetric detection method has been also carried out. Data show a very good linear correlation, proving the effectiveness of the method.