Walter Mitty is a middle-aged, timid suburban man who escapes his mundane life and domineering marriage through elaborate, pulp-fiction-inspired daydreams. He struggles with ordinary tasks, such as moving his car through a parking lot or remembering a shopping list, and often feels emasculated by society. To cope with his sense of insignificance, he imagines himself as various fearless heroes, from a world-renowned surgeon to a dauntless military pilot.

Mrs. Mitty is Walter's domineering and highly practical wife who dictates the couple's routine during their trip into town. She treats her husband much like a child, micromanaging his wardrobe, monitoring his health, and giving him a list of errands to run while she goes to the beauty salon. She serves as the primary tether to reality for Walter, constantly interrupting his heroic reveries with everyday demands.

Dr. Renshaw is Walter Mitty's real-life physician in Waterbury. Though he is simply a practical figure in reality, Walter incorporates him into an elaborate medical daydream where Renshaw is a haggard, desperate surgeon begging the brilliant "Dr. Mitty" to take over an impossible operation.

Wellington McMillan is a millionaire banker and close friend of the president who appears entirely within Walter Mitty's daydream. He suffers from fictitious, life-threatening conditions like "obstreosis" and "coreopsis," requiring the unique, peerless skills of Dr. Mitty to survive.

The parking-lot attendant is an unnamed, assertive worker who forcefully directs Walter Mitty after a driving error. He takes control of Mitty's car, backing it up with an insolent skill that leaves Mitty feeling intimidated and inadequate in the face of competent, younger men.

A young, unnamed mechanic from Walter Mitty's past. When Mitty once failed to remove his car's snow chains and wound them around the axles, this grinning mechanic had to untangle them, creating a lasting memory of humiliation.

A local Waterbury police officer who yells at Walter to get moving when the light turns green. His sharp reprimand flusters Mitty, causing him to hastily put on the driving gloves his wife had demanded he wear.

The District Attorney is an aggressive prosecutor in Walter Mitty's courtroom fantasy. He attempts to badger Mitty about a murder weapon, only to be effortlessly punched in the jaw by Mitty when the courtroom descends into chaos. He represents the real-world bullies who constantly patronize Mitty.

An unnamed, beautiful young woman who throws herself at Walter Mitty during his murder trial fantasy. She acts as a passive, worshipful accessory to his imagined masculinity, offering a sharp contrast to his real-life, domineering wife.