Humor theory has evolved from various disciplines. Numerous professionals have published literature and research studies that examine the historical perspective of humor and the current practice of humor in health care. Historically, researchers have found humor to be an unconscious activity developed from childhood to adulthood. They describe humor as spontaneous and incongruent, involving a changing state of mind. Currently, health care professionals and patients are utilizing humor as a coping mechanism, as a communication skill, and as a tool to promote the psychological and physiological healing process. This article describes how humor theory has evolved, the use of humor in health care, and humor as an adjunct therapy in oncology. Oncology nurses can utilize humor as a part of the nursing process in the care provided to patients and families.