We describe the synthesis and characterization of a novel poly(fluorene-alt-phenylene) substituted with perylenediimide (PDI) moieties as pendant groups. Cyclic voltammetry experiments show the amphoteric nature of the material, which combines the good electron donor ability of the polymeric chain with the acceptor properties of the pendant PDI moieties. Absorption spectroscopy suggests the presence of PDI aggregates, whereas the emission spectra show a strong emission quenching of both the polymeric backbone and the PDI units. Further investigation on the energy and/or electron-transfer processes involved is carried out by temperature-dependent excitation spectra and photoluminescence lifetimes. These studies show the presence of electron transfer not only from the electron donor polymeric chain to the pendant PDI units but also, and more remarkably, to PDI aggregates both in solution and in solid state, as is further confirmed by photoinduced absorption spectroscopy.