A three-dimensional derivative variable-angle synchronous scanning (DVASS) and a synchronous scanning (SS) heavy-atom room-temperature phosphorimetry (HAI-RTP) method are reported, for the first time, to identify and quantify the spectral overlapping phosphorescent pesticides thiabendazole (TBZ) and carbaryl (CBL). These pesticides are widely used in agriculture. The phosphorescence emission of the two compounds was obtained using sodium sulfite as the O2 scavenger and an external heavy atom salt. A careful selection of these experimental variables has been carried out. The increase of selectivity afforded by the DVASS and the SS methodology permitted the demonstration of its applicability to the simultaneous determination of phosphorescent signals of these two pesticides with overlapping spectral profiles. Limits of detection ranged between 1.4 ng/mL for TBZ and 1.7 ng/mL for CBL. The proposed method has been satisfactorily applied to the analysis of both pesticides in different types of water samples.