This work reports a novel and visual method for the simultaneous determination of the chemical (kr) and the physical (kq) quenching rate constants of singlet oxygen (1O2,1∆g) in aqueous media. It is based on the disruption, by a water-soluble substrate S, of the 1O2 chemiluminescence (CL) generated by the H2O2/Na2MoO4 catalytic system. A mathematical analysis of the CL signal at 1270 nm vs time provides separately the overall (kr + kq) and the chemical (kr) quenching rate constants. In ordinary water (H2O), 1O2 lifetime is short and the CL intensity is weak allowing solely the investigation of very reactive substrates for which (kr + kq) > 3 × 106 m−1 s−1 while, in D2O, 1O2 lifetime is significantly longer lifetime and the CL signal is much stronger allowing the study of poorly reactive substrates for which (kr + kq) > 4 × 105 m−1 s−1. The method has been successfully tested on a series of anionic and nonionic water-soluble naphthalene derivatives commonly used as bio-compatible 1O2 carriers. The obtained kr and kq values are in good agreement with the values determined by conventional techniques, namely, flash photolysis and competitive kinetics with a reference quencher.