Tools and interfaces suggesting personalized training are often only sometimes easily accepted and consistently used by aging users. Cognitive ergonomics and inclusive design principles are effective tools for improving the usability and accessibility of graphical interfaces addressed to older people with Parkinson’s disease. The training of gait and posture with digital systems, out of the medical context and without the healthcare professionals’ monitoring, presents several issues impacting the users’ motivation and confidence toward the training method. Cognitive ergonomics and inclusive design principles are effective tools for improving the usability and accessibility of graphical interfaces addressed to older people with Parkinson’s disease. The present paper describes the application of inclusive design methodologies for developing a training interface for older users with Parkinson’s disease, who perform exercises in their living environment. The ongoing design research involved several users in creating the interface options that were then tested and evaluated to define the most accessible and performing ones.