This two-volume set LNCS 14718-14719 constitutes the refereed proceedings of the 12th International Conference on Distributed, Ambient and Pervasive Interactions, DAPI 2024, held as part of the 26th International Conference on Human-Computer Interaction, HCI International 2024, 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 DAPI conference addressed approaches and objectives of information, interaction, and user experience design for DAPI Environments as well as their enabling technologies, methods, and platforms, and relevant application areas. DAPI 2024 covered topics addressing basic research questions and technology issues in the areas of new modalities, immersive environments, smart devices, and much more.