Youths express their own negative experiences and feelings come from their deeply wounded mind. They seek the root cause of these wounded hearts from other people or external environment. Youths revisited the past to heal painful memories. This study designed ontology in order to provide information about the causes and symptoms of illness of the mind for youth counseling. Application ontology enables high-volume and intricate knowledge not only to get set up systematically but also to be stored as the meaningful information. It is also very useful as an integrating tool of the existing complex counseling nomenclature. And ultimately, through revitalization of the sharing and reuse of materials, it becomes possible to provide client-centered counseling services. Therefore, this study built ontology of the mind-illness as a way to analyze the causes and symptoms of the disease in the client mind for providing personalized youth counseling services.