The rich photo-oxidation pathways and products of terrylenediimide (TDI) with singlet oxygen (O-1(2)) have been examined by powerful computational approaches. Potential energy profiles and product fluorescence properties are characterized. A variety of new products are unraveled and predicted to emit fluorescence at both visible and near-infrared ranges, which could open the possibility for interesting applications of using TDI as a fluorescence probe for the single-molecule detection of O-1(2) and designing multicolor photoconvertible fluorophores based on O-1(2) oxidation.