The effects of adding desipramine-containing fluorescence polymer (poly(10,11-dihydro-5-[3-(N-methylamino)propyl]dibenz[b,f]azepine-2,8-diyl-alt-9,9-didodecylfluorene-2,7-diyl, PAzep-Fl) to resins were investigated. When composites were prepared by a reactive blend of poly(lactic acid) (PLA), PAzep-Fl, and diisocyanate, the molecular weight of the obtained composite was larger than that of the composite, which was blended without PAzep-Fl; this suggested that chemical bonding occured between PLA and PAzep-Fl via diisocyanate. The effects of adding PAzep-Fl in two kinds of resins/lysine triisocyanate (LTI) blend were also investigated. The addition of LTI to resins/PAzep-Fl blend composites afforded a shorter wavelength shift of the fluorescence λmax due to the release of the aggregation of PAzep-Fl by LTI. This suggested that the compatibility of two kinds of resins could be estimated by this simple method. The addition of PAzep-Fl to PLA/poly(ε-caprolactone) (PCL)/LTI blends improved the impact strength because of chemical bond formation between PAzep-Fl and the resins (PLA and PCL) via LTI.