Elwood P. Dowd is a mild-mannered, amiable man with an unusual best friend: an invisible, six-foot-tall rabbit named Harvey. Elwood's peculiar behavior and the existence of Harvey cause concern among his socialite sister, Veta Louise Simmons, and her daughter, Myrtle Mae. The situation reaches a tipping point when Elwood disrupts a high-society gathering, prompting Veta to seek his committal to a sanitarium. During the process, a mix-up occurs, leading to the involuntary commitment of Veta instead of Elwood. Dr. Sanderson and nurse Miss Kelly are involved in the confusion, initially believing that Veta is the delusional one.

As the story unfolds, Dr. Chumley, the head psychiatrist, becomes intrigued by Elwood’s claims and the gentle manner in which he speaks of Harvey. As Elwood continues to charm everyone around him, questions arise about the nature of reality, friendship, and the pressures of societal expectations. Those who interact with Elwood start re-evaluating their perspectives on sanity and kindness. Elwood’s unwavering belief in Harvey begins to affect the lives of everyone he encounters, leading them on a journey of self-discovery and contemplation of what genuinely matters in life. The interactions at the sanitarium blur the lines between imagination and reality, creating a heartfelt narrative about acceptance and the unseen influences in our lives.