Gestalt psychology, also known as Gestalt theory, is concerned with the dynamic process of how human beings realize a particular need and obtain this need as a whole. Nurses can apply the fundamental principles behind Gestalt psychology to assist their patients with self-exploration, analysis of the root of a problem and self-behavioral changes. Nevertheless, many nurses, however, do not thoroughly understand the principles on which the theory is based. Using the conceptual analysis in Walk and Avant's study (1995), this paper analyzes the concept of Gestalt psychology. At the same time, the practical meaning of Gestalt psychology is also defined through analysis of related clinical cases. The study aims to provide a solid understanding of Gestalt psychology for psychiatric nurses, which we hope will facilitate their understanding of patients' emotions and behaviors in different clinical cases. We hope, moreover, that after gaining a deeper understanding of Gestalt psychology, these nurses will be able to help patients explore their emotions and achieve desired behavioral changes more effectively. They will also be able to apply concepts of Gestalt psychology not only in the field of mental illness, but also in other fields of healthcare.