In this research work, the optical, electrical, and gas sensing properties of Chloroaluminium Phthalocyanine (ClAlPc) thin film have studied. We fabricated sandwich devices of ClAlPc with aluminium electrodes as Al/ClAlPc/Al, using evaporation deposition method in our Laboratory. SEM analysis was carried out to determine the morphology, grains size and thickness of ClAlPc thin film. UV–vis analysis of thin film indicated B and Q absorption bands of ClAlPc, and its optical band gap was then calculated 3.24 eV. The current-voltage characteristic (I-V) of sandwich devices at different temperatures proved the ohmic and SCLC processes in the ClAlPc thin film. By plotting the LnI versus 1000/T graph, the electrical band gap of ClAlPc was obtained 2.88 eV.In the finally section, the gas sensing behavior of sandwich devices in the presence of CO2 was investigated. To determine the temperature of maximum sensitivity (Tmax), the devices were exposed to CO2 gas over the temperature range 300−450 K at a fixed voltage. We found that Tmax =360 K.