This two-volume set of ITAP 2023, constitutes the refereed proceedings of the 9th International Conference on Human Aspects of IT for the Aged Population, ITAP 2023, held as Part of the 24th International Conference, HCI International 2023, which took place in July 2023 in Copenhagen, Denmark.The total of 1578 papers and 396 posters included in the HCII 2023 proceedings volumes was carefully reviewed and selected from 7472 submissions. The papers of ITAP 2023 Part I are organized in topical sections named: Designing and Assessing the Older Users' Experience; Aging and Social Media; Voice Assistants and Chatbots; Games and Exergames for Older People.