We investigated the grain refinement effect on the resistance to hydrogen embrittlement in an equiatomic CoCrFeMnNi high-entropy alloy. In a 100 MPa hydrogen gas pre-charging condition, grain refinement to 1.9 mu m improved the hydrogen embrittlement resistance in terms of the strength-elongation balance. In particular, the tensile strength of the grain refined high-entropy alloy did not decrease by hydrogen uptake. However, when the sigma phase formed at a relatively low temperature, both the strength and elongation decreased due to hydrogen charging. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.