A concept of the interface adhesion energy, Γ0, has been proposed to characterize the quality of interface adhesion of the elastic–plastic materials system. A geometrically nonlinear finite element analysis of a blister test of an elastic–plastic film bonded to an elastic–plastic substrate has been conducted. The fracture process ahead of the crack tip at the interface between the thin film and the substrate is represented in terms of a built-in cohesive model, for which interface adhesion energy and the peak stress required for separation are basic parameters. Effects on the critical pressure of various influencing parameters are studied. The plastic work in the substrate contributes significantly to the critical pressure. Agreement between modeling prediction and measurement evidences the validity of the proposed concept and the method of extracting the interface adhesion energy.