U.S. Marshals picked up Charman Sinkfield about 9 p.m. driving a black sedan on Interstate 20, wearing a wig that gave the appearance of dreadlocks, said James Ergas of the service's fugitive task force.
Sinkfield was charged with murder, felony murder, aggravated assault, possession of a firearm during the commission of a felony and possession of a firearm by a convicted felon, said Atlanta police Lt. Keith Meadows.
Ergas said officers had been trailing Sinkfield and captured him after they set up a rolling roadblock on the freeway.
"It's been a very exhausting investigation. We were able to catch him with a lot of hard work," Ergas said.
Sinkfield's attorney, John Ash, was on his way to the Atlanta police headquarters and was not immediately available for comment.
The 38-year-old Forrest was shot to death on July 25 after he chased a man who robbed him of his championship ring and Rolex watch.
Two other men have been arrested in the case, but police believe neither of them shot Forrest.
Forrest, a native of Augusta, Ga., who lived in Atlanta, was a member of the 1992 Olympic team along with Oscar De La Hoya. The fighter later won welterweight and junior middleweight titles and compiled a professional record of 41-3 with 29 knockouts.