This paper proposes a method for developing harmonic cantilevers for tapping mode atomic force microscopy (AFM). The natural frequencies of an AFM cantilever are tuned by inserting gridiron holes with specific sizes and locations, such that the higher order resonance frequencies can be assigned to be integer harmonics generated by the nonlinear tip–sample interaction force. The cantilever is modeled using the vibration theory of the Timoshenko beam with a nonuniform cross section. The designed cantilever is fabricated by modifying a commercial cantilever through focused ion beam (FIB) milling. The resonant frequencies of the designed cantilever are verified using a commercial AFM.