The quantitative analysis of trace water in organic solvents remains a hotspot in current research because of the importance in both industrial and laboratory scale chemistry. This study introduced a fluorescence chemosensor (L3) for the detection of trace water in dimethyl sulfoxide (DMSO). Addition of water into the DMSO solution of L3 resulted a significant fluorescence enhancement at 533 nm with a detection limit of 0.002 wt%. The fluorescence turn-on response is occurred due to the formation of aggregates of L3. Also, other possible mechanism for trace water detection by L3 in DMSO is attributed to the specific water-L3 interaction and partially to the increase in polarity of the solvent caused by an increase in water concentration. Dynamic light scattering (DLS), 1H NMR, scanning electron microscope (SEM), transmission electron microscope (TEM) and quantum mechanical studies were performed to support the water sensing by L3 in DMSO. © 2021