Cotton defeated State Sen. Gene Jeffress, of Ouachita County, the Green Party's Joshua Drake and Libertarian Party candidate Bobby Tullis.
Cotton had 59-percent of the vote and Jeffress had 37-percent while Tullis and Drake each had 2-percent, with 91-percent of precincts reporting.
Cotton, a Republican and native of Dardanelle is a Harvard-educated attorney, Iraq-Afghanistan veteran and marathon runner.
He fills the seat held for 12 years by Rep. Mike Ross, who leaves public service in January.
A sixth-generation Arkansan, Cotton was born and raised in Dardanelle on his family's cattle farm.
Cotton's military decorations include the Bronze Star Medal, Ranger Tab, Combat Infantryman Badge, Parachutist Badge, Air Assault Badge, Afghanistan Campaign Medal, and Iraq Campaign Medal.
Following his active-duty service, Tom worked as a management consultant for McKinsey and Company. As a businessman, Tom has advised some of America's most respected companies on business strategy, operations, finance, and marketing. His industry experience includes agribusiness, health care, oil and gas, food processing, insurance, and aerospace.
The Fourth District covers 29 counties in Central, South and Western Arkansas, including:
Ashley, Bradley, Calhoun, Chicot, Clark, Cleveland, Columbia, Dallas, Desha, Drew, Garland, Grant, Hempstead, Hot Spring, Howard, Jefferson, Lafayette, Lincoln, Little River, Logan, Miller, Montgomery, Nevada, Ouachita, Pike, Polk, Scott, Sevier, and Union.
Cotton will take his oath of office in Washington in January.