 Since the 2017–18 season, Hornkamp has been part of the first team squad at SC Heerenveen.He made his debut for SC Heerenveen in the playoffs for the UEFA Europa League on 9 May 2018, in the home match against FC Utrecht, which was won 4–3.He came on the field as a substitute for Reza Ghoochannejhad the 88th minute.