This two-volume set LNCS 14017 - 14018 constitutes the thoroughly refereed proceedings of the 20^th International Conference on Engineering Psychology and Cognitive Ergonomics, EPCE 2023, held as part of HCI International 2023 which took place in Copenhagen, Denmark, during July 23-28, 2023.

A total of 1578 papers and 396 posters have been accepted for publication in the HCII 2023 proceedings from a total of 7472 submissions.

The papers included in the HCII-EPCE volume set were organized in topical sections as follows:

Part I: Stress, fatigue, and mental workload; human performance and error management; resilience and performance in demanding contexts.

Part II: Human factors in aviation; human factors in operations management; human-centered design of autonomous systems.