We report the first measurements of the linear thermal expansion coefficient &agr;tof hydrogenated amorphous Ge thin films. We have utilized optical reflection interference fringes to measure the gap between the film and a fused quartz substrate in a segment of the film which lifted from the substrate due to intrinsic compressive strain. The linear thermal expansion coefficient of &agr;t=1.7×10−5K−1for 300 K <T< 420 K is ∼3 times larger than that of crystalline Ge.