The aggregation behavior of the zinc porphyrin-beta-CD conjugate in a water/ethanol binary mixed solution was investigated. The spectroscopic data and the atomic force microscopy (AFM) image strongly suggest that a part of a Zn porphyrin is included in the beta-CD nanocavity of another ZnP-beta-CD conjugate at certain concentrations, leading to the formation of Zn porphyrin J-aggreates.