This book constitutes the refereed proceedings of the 18th International Conference on Engineering Psychology and Cognitive Ergonomics, EPCE 2021, held as part of the 23rd International Conference, HCI International 2021, held as a virtual event, in July 2021. The total of 1276 papers and 241 posters included in the 39 HCII 2021 proceedings volumes was carefully reviewed and selected from 5222 submissions. EPCE 2021 includes a total of 34 papers; they were organized in topical sections named: cognitive psychology in aviation; cognitive psychology in air traffic control; studies on cognitive processes; human error and human performance; and cognition and design.