Following his arrival, he was reunited with former West Ham United teammate, Ashley Fletcher, who signed for Middlesbrough on 28 July. On 1 August 2017, it was confirmed that Randolph would wear the number 25 shirt for the 2017–18 season. Randolph made his league debut for Middlesbrough on 5 August 2017 away to Wolverhampton Wanderers, which resulted in a 1–0 defeat. He held his first clean sheet the following week, when his team won 1–0 to division newcomers Sheffield United at the Riverside Stadium. He held a second consecutive clean sheet in their next fixture, a 2–0 victory at home against Burton Albion. In March 2019 he was selected to the 2018–19 Championship Team of the Season. On 15 January 2020 it was announced that Randolph was returning to West Ham following an agreement with Middlesbrough. Randolph has represented the Republic of Ireland at U15, U16, U17, U18, U19, U21, B, and senior levels. He was called up to the Republic of Ireland senior squad for the first time in March 2011 for a match against Macedonia. He was again called up in May, for match against Northern Ireland and Scotland in the Nations Cup, but again did not feature. Randolph made his full international debut in a friendly against Oman on 11 September 2012, coming on as a substitute in a 4–1 win. His second Republic of Ireland appearance was against Spain on 12 June 2013, again as a substitute; he made a "brilliant fingertip save" from Santi Cazorla before conceding a late goal by Juan Mata as Spain won 2–0. On 8 October 2015, Randolph replaced Shay Given in the 44th minute against Germany in a 2016 European Championship qualifying match and provided the long ball assist for Shane Long's winner in the 70th minute in a match won 1–0 by the Republic of Ireland. Randolph played every match for the Republic of Ireland at Euro 2016, against Sweden, Belgium and Italy before being defeated by France. His father Ed Randolph played basketball for UCD Marian and was one of the first American imports to the Irish Basketball League. His mother, Anne Randolph, is a folk singer. He is a past pupil of St. Cronan's Boys National School and Presentation College, Bray. He had a long-term relationship with Rochelle Wiseman from girl group The Saturdays. Accrington Stanley  Motherwell  Individual