The number of passages in the high-pressure homogenizer affected the dimensions and the surface charge of the resulting nanoparticles. Increasing number of passages in the homogenizer raised the zeta potential from -16.1 to -44.1 mV; the aspect ratio decreased from 42.7 to 15.1. The crystallinity of the treated banana fibers increased by 300 %. FTIR spectra of the cellulose nanofibers confirmed that the treatment effectively removed most of the hemicellulose and lignin components. The nanofiber samples exhibited enhanced thermal properties; thermal stability increased as a function of the number of passages in the homogenizer.