The two volume set LNCS 16574 and 16575 constitutes the proceedings of the International Work-Conference on the Interplay Between Natural and Artificial Computation, IWINAC 2026, held in Canary Islands, Spain, during May 26–29, 2026. The 93 full papers included in this book were carefully reviewed and selected from 187 submissions. They were organized in topical sections as follows:Part I: Machine Learning in Neuroscience; Functional Evaluation of Neuromotor and Cognitive Disorders; Intelligent Systems for the Study and Support of Youth Mental Health; Socio-Cognitive, Affective and Physiological Computing; Intelligent Systems for Assessment, Treatment, and Assistance in early stages of Alzheimer; Neuroprosthesis, Ethics; and European Culture and Technology Lab;Part II: Machine Learning in Computer Vision and Robotics; Robotics; Bio-Inspired Computing Approaches; Social and Civil Engineering through Human AI Translations; Explainable, Robust and Trustworthy Machine Learning and its Applications; Learning tools to lecture; and Other Applications.