A graduate of Stilwell High School, Mullin went on to attend Missouri Valley College on a wrestling scholarship until the age of 20 years old. At that time, Senator Mullin's father, Jim, fell ill, and Mullin and his recent bride Christie postponed studies to take over the family business, Mullin Plumbing.

Over the past 25 years, Markwayne and Christie Mullin have expanded Mullin Plumbing to become the largest service company in the region, and along the way founded numerous other successful companies ranging from Mullin Environmental to Rowan's Steakhouse, the latter a bustling restaurant in the neighboring town of Stilwell and named for Christie's family.

As one of the only current business operators in the U.S. Senate, Mullin brings over 25 years of firsthand experience and entrepreneurial leadership to address some of the biggest issues impacting the U.S. economy and Oklahoma's small business community.

Senator Mullin is an enrolled member of Cherokee Nation and is the first Tribal citizen to serve in the U.S. Senate in nearly two decades. He is the second Cherokee Nation citizen to ever serve in the chamber.

Markwayne Mullin is a former undefeated Mixed Martial Arts (MMA) fighter with a professional record of 5-0. He was inducted into the Oklahoma Wrestling Hall of Fame in 2016. Mullin has remained active in the wrestling community since his retirement from the sport, continuing to coach his children and other young athletes in wrestling tournaments across the country on weekends through today.

In 2010, Senator Mullin completed his university education and received his degree in Applied Science in Construction Technology from Oklahoma State University Institute of Technology. He received an honorary doctorate degree from Bacone College in 2018.