The wetting behavior of a polymer liquid on a coated substrate is investigated via numerical self-consistent field calculations and experiments. The polymer does not wet the coated substrate, but the substrate might stabilize a mesoscopic film. Experiments observe a stable mesoscopic film of nanometer thickness in coexistence with macroscopic drops at high temperatures. Upon cooling, this mesoscopic polymer film breaks up into droplets (nano-dewetting). Our self-consistent field calculations suggest that the stability of the mesoscopic film is determined by a subtle interplay between van der Waals forces and short-ranged forces due to the distortion of the profile in the vicinity of the substrate.