This book constitutes the refereed proceedings of the 13th International Conference on Augmented Cognition, AC 2019, held as part of the 21st International Conference on Human-Computer Interaction, HCII 2019, in Orlando, FL, USA in July, 2019.  The 1274 full papers and 209 posters presented at the HCII 2019 conferences were carefully reviewed and selected from 5029 submissions. The papers cover the entire field of human-computer interaction, addressing major advances in knowledge and effective use of computers in a variety of applications areas. The papers in this volume are organized in the following topical sections: cognitive modeling, perception, emotion and interaction; human cognition and behavior in complex tasks and environments; brain-computer interfaces and electroencephalography; and augmented learning.