White electroluminescence (EL) was observed for the first time in the hydrogenated amorphous silicon‐carbon alloya‐SixC1−x@B:H(x=0.2–0.4) at room temperature. Experiments were carried out for the devices which consisted of an amorphous film sandwiched between two insulating layers of Y2O3. EL is observable above a threshold ac voltage of 100 V. The EL spectrum is slightly different from the photoluminescence spectrum of the amorphous film.