Effective fresh coal flotation can be achieved using conventional hydrocarbon oily collectors while oxidized coal flotation can be enhanced using oxygen-containing fatty acid. Solid-state paraffin and stearic acid were selected to represent a hydrocarbon oil and fatty acid collector in the present study, respectively. The interaction forces between paraffin/stearic acid and fresh/oxidized coal particles were measured directly using atomic force microscopy (AFM) colloidal probe technique. Flotation experiments with hydrocarbon oil (dodecane) and fatty acid (oleic acid) were carried out to validate the AFM results. The results show that a pure attractive force was detected between fresh coal and paraffin while a slightly repulsive force before the jump-into contact was observed between fresh coal and stearic acid. Effective fresh coal flotation can be achieved by using both dodecane and oleic acid, while the recovery with dodecane was always higher than that of oleic acid. In contrast, a significant jump-into contact between oxidized coal particles and stearic acid was found while a monotonous repulsive force between oxidized coal and paraffin. 77.76% oxidized coal flotation recovery was obtained when 700 g/t oleic acid was used, much higher than that of dodecane. The outcome of the present study can give a basic understanding of unoxidized/oxidized coal collector interactions and provide guidance for coal flotation engineering.