While still at Cowdenbeath, Nicholl had also become assistant manager to Michael O'Neill with the Northern Ireland national team in March 2015.[18] He was appointed as assistant to new Falkirk manager Paul Hartley in October 2017, while also continuing in his role with Northern Ireland.[19] He became assistant manager at Rangers in January 2018, assisting Graeme Murty.[20] After Murty left Rangers on 1 May, Nicholl and Jonatan Johansson were placed in interim charge[21] until the appointment of Steven Gerrard on 1 June.