The development of room temperature organic magnets is long viewed as great challenge in chemistry, physics, materials science, and spintronics. Here, room temperature ferromagnetic properties of rare earth Sm-doped tris (8-hydroxyquinoline) gallium (GaQ(3)) molecular thin films prepared by thermally co-evaporating Sm metals and GaQ3 powders were reported. X-ray photoelectron spectrometer, Fourier transform infrared spectroscopy and density functional theory analysis suggest that the doped Sm atom bonds with N atoms on different hydroxyquinoline ligands. The room temperature ferromagnetism is attributed to the extremely large energy difference (594 meV) between the ferromagnetic ground state and the antiferromagnetic state. Furthermore, photoluminescence experiments show that the films emit green light at room temperature. Our experiments may be helpful for the development of molecular ferromagnetic optoelectronic materials for the use of novel multifunctional optoelectronic and spintronic devices.