Nanoparticles of 4-(dicyanomethylidene)-6-(4-dimethylaminostyryl)-2-methyl-4H-pyran (DCM) red fluorescent dye were prepared using a reprecipitation method. The absorption spectra of DCM nanoparticles showed that compared to the absorption spectrum of a diluted solution, the intramolecular CT peak was blue-shifted due to H-aggregation. In addition, the fluorescence quenching of DCM nanoparticles was observed, resulting from H-aggregates and the twisted conformations of chromophores in the nanoparticles.