The effect of graphene overlayers on metal-chloride-doped graphene (D-G) against thermal annealing was investigated. Pristine graphene and D-G were used as overlayers on D-G in a layer-by-layer method. The decrease of transmittance was happened in D-G regardless of overlayers after thermal annealing. It is shown that the reduction of the transmittance by thermal annealing comes from the aggregation of metal cations. The sheet resistance of D-G without overlayers increased from 460 Omega/sq. to 24,473 Omega/sq. after thermal annealing at 400 C. However, the increase of sheet resistance and decrease of work function were suppressed with thermal annealing in the sample with overlayers, especially for more than 3 overlayers. The G band position in Raman spectroscopy of D-G with overlayers was almost maintained in the doped state even after thermal annealing. The decrease of chlorine ion contents in D-G with overlayers was suppressed compared to those in D-G without overlayers after thermal annealing. Therefore, it is thought that graphene overlayers on D-G are effective to suppress the evaporation of chlorine ion, extending the thermal stability. (C) 2014 Elsevier B.V. All rights reserved.