An ethylene-propylene random copolymer (EP) was maleated according to two different procedures which were expected to yield different distributions of succinic anhydride (SAH) along the backbone. The two maleated EPs, referred to as EP-I and EP-II, were labeled with fluorescent dyes such as pyrene and/or naphthalene by reacting 1-pyrenemethylamine (or 1-naphthalenemethylamine) with the SAH moieties randomly attached along the EP copolymer. As a result, the distribution of dyes mimics that of the SAH moieties along the polymer backbone. The labeled EP copolymers thus obtained were studied by steady-state and time-resolved fluorescence techniques in solution. Hexane and tetrahydrofuran (THF) were chosen as solvents. Pyrene excimer formation and fluorescence resonance energy transfer measurements were performed to demonstrate that the SAH moieties are attached to EP-I in a less clustered manner than to EP-II. These conclusions were confirmed by analyzing the fluorescence decays of the pyrene-labeled EPs with a blob model developed in the laboratory. Viscosity measurements were performed on both pyrene-labeled EP copolymers to evaluate the effect that SAH clustering has on the solution properties of the polymers in hexane. The solution viscosity of the pyrene-labeled EP-I increases less steeply with polymer concentration than that of the pyrene-labeled EP-II. This effect is due to the higher SAH clustering observed with EP-II, which leads to a more efficient formation of interpolymeric aggregates held together via dipolar associations between the anhydride moieties. This study establishes that fluorescence can be applied to investigate the microstructure of maleated EP copolymers and that SAH clustering of a maleated EP copolymer can affect its properties in apolar solvents.