Communication: ABA triblock copolymers consisting of different carbazole-containing blocks and ruthenium complexes were designed with respect to their energy-transfer behavior. The number of 2-vinylpyridine (2VP) units in a polymer chain was tailored from 0 to 20 to observe the size effect of the metal complex as a luminophore or as a luminescence quencher. Photoluminescence and optical absorption measurements as well as the intermolecular energy transfer in the block copolymers were studied. Evidence is provided for a fast energy transfer from carbazole to the ruthenium-coordinated 2VP.