Quaternary Co2FeAl0.Si0.5 Heusler alloy thin films have attracted special attention for the application in magnetoelectronic devices. Co2FeAl0.5Si0.5 alloy thin films are fabricated by magnetron sputtering at room temperature. The temperature effects on the magnetic, electrical and optical properties in sputtered Co2FeAl0.5Si0.5 alloy films are investigated. Thermomagnetic measurements reveal increased magnetization arising from enhanced crystalline ferromagnetic ordering. Anomalous increase in electrical resistivity with temperature is probed in the alloy film, accompanied with significant change in optical reflectance. The large variations in electrical and optical signals in the alloy film can be attributed to the transition of atomic orderings, confirmed by X-ray diffraction measurements. The activation barrier for the transformation of atomic orderings is determined to be 1.22 eV, showing good thermal stability of the Heusler alloy thin film. (C) 2018 Elsevier B.V. All rights reserved.