This book constitutes the refereed proceedings of 6th International Conference on Adaptive Instructional Systems, AIS 2024, held as part of the 26th International Conference, HCI International 2024, which took place in Washington, DC, USA, during June 29-July 4, 2024. The total of 1271 papers and 309 posters included in the HCII 2024 proceedings was carefully reviewed and selected from 5108 submissions. The HCII-AIS 2024 contributions have been organized in the following topical sections: Designing and developing adaptive instructional systems; adaptive learning experiences; AI in adaptive learning.