The purpose of this study is to investigate the effects of Mn addition on the microstructure, mechanical properties, and electrochemical corrosion properties of Al0.3CoCrFeNiMnx (x = 0, 0.1, and 0.3) high-entropy alloys. All alloys are simple face-centered cubic solid solutions. After addition of Mn to the Al0.3CoCrFeNi alloy, the lattice parameter and hardness increase from 3.591 angstrom to 3.611 angstrom and from HV141 to HV156, respectively. Meanwhile, the yield stress and ultimate tensile strength increase from 119 MP to 158 MPa and from 295 MPa to 371 MPa, respectively. The increase in yield stress is due to solid solution strengthening, and the increase in ultimate tensile strength results from the increase in work hardening due to the reduction of stacking fault energy. Polarization curves of the alloys show that the corrosion resistance slightly decreases after additions of Mn. (C) 2017 Elsevier B.V. All rights reserved.