Chad Douglas, a successful western horse trainer, is facing a six-hour drive back to his home, Horse Haven Ranch, when he receives a call from a friend begging him to come to the aid of a damsel in distress. The damsel in question is Cassandra Davidson, and her distress is the desperate need for someone to drive her horses to a five-day show-jumping event in which she is competing.

Chad has heard that Cassandra is a spoiled princess who can be difficult and demanding, but he has also heard she has a unique appeal that is truly endearing. His curiosity is piqued, and since the show is being held close to his ranch, he decides to come to her rescue. Though sparks fly when they first meet, their long road trip begins—but with a stern warning from Chad: "What you need is an old-fashioned spankin', and if you don't get your head on straight I'll be happy to oblige."

As their story unfolds, Chad discovers there is more to "Sassy Cassie" than he first thought, and she is utterly captivated by the handsome, no-nonsense cowboy. But Chad lives by a set of rules, and if Cassie wants to spend time with him, she has to follow them or face the consequences.

The Cowboy's Rules is an old-fashioned love story about a strong-willed cowboy who has no qualms about yanking a disobedient female across his lap and an equally strong-willed, defiant young woman who thinks she's smarter than the average bear. She is, but so is he.