A narrow‐band emission has been detected at room temperature during the pulsed on state of a well‐characterized threshold switching material, amorphous Te39As36Si17Ge7P1. The luminescence peak is centered around 0.55±0.03 eV, very close to half of the optical band gap of this material, 1.1 eV. This ratio of luminescence peak to optical band gap is similar to that obtained from the photoluminescence of a large class of chalcogenide glasses in their off states, strongly suggesting that the origins of the on‐state electroluminescence and off‐state photoluminescence are the same. The electroluminescence exhibits a threshold behavior, appearing only for on‐state currents in excess of 4 mA. The output follows a Lambertian law for solid angles up to about 0.7 sr, and slowly deviates below the Lambertian law at larger solid angles. The width of the luminescence line is less than 0.1 eV, indicating that its origin cannot be blackbody radiation. This provides another confirmation of the electronic nature of threshold switching.