Phenanthrene-label ed poly(styrene-b-poly(ethylene-co-butylene)-b-polystyrene triblock copolymers (SEBS) have been prepared from a maleated derivative of the polymer. The dye was attached either through an imine or an ester linkage. The model compound 4, N-phenanthrylmethyl succinimide, exhibits an exponential fluorescence decay in deaerated THF solution, with a lifetime of tau(0) = 4.5 ns. However, the fluorescence decays of the labeled SEBS polymers, both in film and in solution, could only be fitted with a sum of three exponential functions, with lifetimes approximately equal to 2, 14, and 44 ns. The long lifetime coincides with that of unquenched phenanthrene. The shortest lifetime, 2 ns, was attributed to polystyrene (PS) emission and could be corrected using the decay of the PS component of unlabeled SEBS (tau(PS) approximate to 2 ns). The 14 ns lifetime appears to be a result of phenanthrene self-quenching brought about by local aggregation, driven not by the dye itself but by the functional group used to attach the dye to the polymer, the succinimide group or the -COOH groups of the succinate monoester derivative. Upon full methylation of the acid groups in the phenanthrylmethyl-ester-labeled SEBS copolymer, the interaction between the acid groups is removed and the extent of phenanthrene aggregation is strongly reduced. After correction for the PS emission, the phenanthrene decay profiles of the fully methylated SEBS copolymer, both in solution and in the film, could be fitted with only one exponential.