The aim of this study is to investigate the effectiveness of mixed reality (MR)-based rehabilitation applications in improving motor functions, trunk stability, and upper extremity performance in stroke patients. The use of mixed reality technology in addition to traditional rehabilitation methods provides individuals with an interactive and motivating rehabilitation environment that mimics real-life activities. The study aims to increase functional independence, improve motor skills and trunk stability, enhance upper extremity functions, facilitate return to daily living activities, increase adaptation and motivation to the rehabilitation process, and provide a repeatable, safe, and patient-centered exercise environment in stroke patients. This thesis aims to contribute to both clinical physiotherapy practice and the literature by evaluating the applicability of mixed reality technology, a patient-centered and innovative rehabilitation approach, as a treatment option in neurological rehabilitation. The study's objective in improving upper extremity function is to make the individual less dependent on others while performing daily living activities, to instill a sense of self-sufficiency, and to enhance existing skills to make them more functional.