Orthorhombic In 2Mo 3O 12 has low negative linear coefficient of thermal expansion ( α l = −1.85 × 10 −6 °C −1) as evaluated by X-ray powder diffraction using a synchrotron facility. The linear coefficient of thermal expansion for orthorhombic In 2Mo 3O 12 is directly dependent on the inherent volume distortion parameter ( υ) of InO 6. This finding strongly corroborates the recently proposed relationship between the linear coefficient of thermal expansion in A 2 M 3O 12 compounds ( α l) and the distortion level of AO 6 polyhedra. With the increase of inherent distortion parameter ( υ) of AO 6 polyhedra, the linear coefficient of thermal expansion becomes more negative. Another important feature of AO 6 polyhedra, including InO 6, is that their distortion increases as a function of temperature. Orthorhombic In 2Mo 3O 12 is stable in the studied temperature range, 370–760 °C.