This textbook provides a fundamental introduction to therapeutic and special educational diagnostics. Initially, the goals, tasks, and limitations in educational fields are presented, and the diagnostic process is outlined. Various diagnostic methods for gaining insights are then introduced, and the diagnostic actions are related to framework theories. The third part of the book discusses practical applications, including support plans, legal foundations, necessary qualifications, and ethical aspects of diagnostics. Practical examples establish a direct connection to therapeutic and special educational work and are reflected upon. The book serves as an overview of topics and content related to therapeutic and special educational diagnostics and imparts practical competence. Contents include: I. Basics.