An improved vibrating‐reed method is described for determining Young's modulus of thin films deposited on both sides of a substrate. This technique consists of measuring the resonant frequency of a cantilever composite beam obtained by coating both sides of a substrate. The calculation procedure is presented to evaluate the film modulus from sample geometry, material density, and mechanical resonant frequency. For accurate determination of resonant frequency, the phase angle between the exciting and vibration signals is analyzed. Using the proposed technique, Young's modulus of ZrO2thin films is calculated, obtaining a value in agreement with literature dat