Abstract: The flotation kinetics of different size fractions of conventional and nanobubble (NB) flotation were compared to investigate the effect of NBs on the flotation performance of various coal particle sizes. Six flotation kinetics models were selected to fit the flotation data, and NBs were observed on a hydrophobic surface under hydrodynamic cavitation by atomic force microscope scanning. Flotation results indicated that the best flotation performance of size fraction at −0.125+0.074 mm can be obtained either in conventional or NB flotation. NBs increase the combustible recovery of almost all the size fractions, but they increase the product ash content of −0.25+0.074 mm and reduce the product ash content of −0.045 mm at the same time. The first-order models can be used to fit the flotation data in conventional and NB flotation, and the classical first-order model is the most suitable one. NBs considerably enhance flotation rate on coarse size fraction (−0.5+0.25 mm) but decrease the flotation rate of the medium size (−0.25+0.074 mm). The improvement of flotation speed on fine coal particles (−0.074 mm) is probably the reason for the improved performance of raw sample flotation.