Williamson was one of the first assistant coaches hired by the Panthers and was a mainstay on the coaching staff for 15 years before retiring after the 2009 season. He worked under three head coaches – Dom Capers, George Seifert, and John Fox – and was regarded as one of the best teachers in the NFL.
Wide receivers coach for all but one of his 15 years with the Panthers, Williamson helped develop Steve Smith, Muhsin Muhammad and Rocket Ismail while coaching a number of other players, including Mark Carrier and Willie Green, to their most productive professional seasons.