The discovery of magnetostriction at room temperature in the antiperovskite Mn3SbN is reported herein. Mn3SbN undergoes a phase transition from a high-temperature (high-T) paramagnetic state to a low-Tferromagnetic (FM) state at the Curie temperature ofTC= 360 K, accompanied by a cubic-to-tetragonal structural deformation. In the tetragonally distorted FM phase, Mn3SbN exhibits large magnetostriction of up to 450 ppm, estimated from the linear thermal expansion under a magnetic field of 90 kOe while slowly reducing the temperature. The magnetostriction estimated by the same procedure is enhanced to 1000 ppm without reduction of the operating temperature by partial replacement of the constituent elements. The present results are examined in terms of ferromagnetic shape memory effects.