On 21 November 2014, he refereed his first professional game, Connacht v Zebre during the 2014–15 Pro12 season. That season, he also made his international debut, refereeing Belgium v Sweden during the 2014–16 European Nations Cup Division 1B season. At the end of that season, Whitehouse signed a professional referee's contract with the WRU on the 5 June 2015, just a day before he refereed his first World Rugby Under 20 Championship match, between France U20 and Japan U20.