Amorphous Co 2 MnSi thin film was deposited using radio-frequency sputtering. The amorphous film crystallized into a single-phased L2 1 structure at 500°C, which was highly disordered. The structure was meta-stable as the crystallized film decomposed upon further heating. Increasing the annealing temperature to 600°C precipitated fcc Co together with Co 2 MnSi. Magnetic measurements showed that the as-deposited amorphous film was paramagnetic, exhibiting a spin glass state below 44K. The phase transition at 500°C produced a ferromagnetic Co 2 MnSi thin film whose saturation magnetic moment was considerably lower than reported values due to the disordered structure of the crystallized film.