It is well known that a thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) becomes turbid above a cloud point (CP) temperature. In this study, the phase transition changes of PNIPAM end-functionalized with pyrenyl group (Py-PNIPAM) were investigated in dilute aqueous solutions. Two types of Py-PNIPAMs were prepared; one is an ester-linkage type (Py-OCO-PNIPAM), and the other an amide-linkage type (Py-NHCO-PNIPAM). From temperature dependence of fluorescence and fluorescence-excitation spectra for these polymer solutions, the micelle-like aggregates formation was found to be more favorable in Py-OCO-PNIPAM. To elucidate the cause of the difference, the partial dipole moments (PDM) of end-pyrenyl groups was obtained by molecular orbital calculations. The PDM value of the ester linkage type was smaller than that of the amide linkage type. The smaller value of PDM in the ester linkage type may explain the reason for the higher ability to form a micelle of Py-OCO-PNIPAM if the pyrenyl groups are assumed to be the core in the micelle.