Pyrene-labeled hydroxypropyl cellulose (HPC-Py) was synthesized through a condensation reaction between hydroxypropyl cellulose (HPC) and 1-pyrenebutyric acid (Py). A hybrid (HPC/MWNTs) of the HPC-Py and multiwalled carbon nanotubes (MWNTs) was prepared through a noncovalent method. Temperature-variable UV-vis spectra indicated that the HPC-Py had a lower critical solution temperature of about 44 degrees C in water. H-1 NMR, UV-vis, Raman, and fluorescence spectra were used to systematically investigate the pi,pi stacking interaction between the HPC-Py and MWNTs. Dispersion experiments showed the HPC/MWNTs hybrids could be well dispersed in water and many organic solvents.