The effect of different mold coatings on the ejection force in micro injection molding was experimentally investigated for a selection of thermoplastic polymers, at different molding conditions. Diamond like carbon (DLC), chromium nitride (CrN) and chromium titanium niobium nitride (CrTiNbN) coatings were selected in accordance with their potential affinity with the considered injected polymers. A specific mold cavity was designed, manufactured by micro milling and characterized (both topography and geometry) in order to isolate the effect of polymer adhesion on the ejection force. The obtained results were then correlated with the adhesion work for all the combinations of injected polymers and surface coatings. The wettability analysis was performed by measuring the interface contact angle at the melt temperature. The results indicated how an optimum mold coating, which minimizes the ejection force for a specific polymer, should be selected considering its wettability properties.