This four-volume set LNCS 16108-16111 constitutes the proceedings of the 20th IFIP TC 13 International Conference on Human-Computer Interaction, INTERACT 2025, held in Belo Horizonte, Brazil, during September 8–12, 2025. The 69 full papers, 34 short papers and 79 papers of other types included in this book were carefully reviewed and selected from 330 submissions. They were organized in topical sections as follows: Part I: Accessibility; Adaptive and AI-Powered Learning Systems; Aesthetics in HCI; Affective HCI and Emotion; and Augmented Reality. Part II: Computer-Supported Cooperative Work; Context-Dependent Systems; Design and Evaluation in Smart and Ubiquitous Contexts; Designing for Identity, Safety, and Cultural Values; Emotionally-Informed Design; HCD for Mission-Critical Systems; HCI in Formal and Inclusive Learning Contexts; HCI in Healthcare and Wellbeing; and Human-AI Interaction. Part III: Interaction with Small or Large Displays; Learning Tools and Intelligent Tutoring; Methodologies for HCI; Multimodal Assistive Interfaces; Usability Evaluation Methods; Usable Privacy and Security. Part IV: Courses; Industrial Experiences; Interactive Demonstrations; Panels; Posters; and Workshops.