Polymer films containing cationic cyanine dye, 1,1’-diethyl-2,2’-cyanine chloride (PIC), were fabricated by dropping aqueous solutions of the dye and the water-soluble polymer on the quartz plate and drying. The aggregation state of PIC in thin polymer films was dependent on the kind of polymers. The aggregation state could be controlled by varying the amount of anionic sites on the polymer chain or by mixing two kinds of polymers.