Don was a member of the North Texas State golf team that won four consecutive NCAA Division I titles from 1949-52. He graduated in 1953 after which he went into the Air Force.
Don maintained his golf game while in the Air Force. At the end of his service in 1956, he became a Tour professional. He won a total of 10 PGA Tour events including the 1967 PGA Championship.
In the period between his last PGA Tour win and the start of the Senior PGA Tour, January devoted most of his professional efforts to a golf course design business, JanMart Enterprises, that he had established with fellow Texan and PGA Tour golfer Billy Martindale.
He won the first official event on the Senior PGA Tour, the 1980 Atlantic City Senior International. He is well known for his success on the Senior PGA Tour (now the Champions Tour), winning 22 events including two PGA Seniors' Championships.