 He was promoted to the first team in 2016, where he signed his first professional deal with the club.On 31 August 2016, Marcussen made his official debut for Lyngby, starting in a 3–1 win in the Danish Cup over Frederiksværk FK in the second round.Marcussen made his Danish Superliga-debut for Lyngby on 18 May 2017 in a match against Brøndby IF.