After earning his MBA, Johnson spent 13 years with Colgate-Palmolive. In 1973, he joined Warner-Lambert Corporation, where he was named president and CEO for the Entenmann's division. He joined General Foods Corporation as vice president and later served as chairman, president, and CEO at Gerber Products Company. In 1990, Johnson was named president and CEO of the Campbell Soup Company. By 1992, he also was a member of the board of directors.
Known as a no-nonsense, aggressive business leader, he was noted for turning around both Gerber and Campbell. Key to his turnaround formula, which involved decisiveness, ability to forge consensus, and motivating employees, was his ability to articulate a goal and focus company resources on it.
Johnson served as director of the Colgate-Palmolive Company and was a member of the American Bankers Association and the Grocery Manufacturers of America.