In 2013, he took part in a trial with Eredivisie club PSV Eindhoven but ultimately remained with Midtjylland's youth team.
[4] During his time with the U19 group, Duelund won the Top Goalscorer and Player of the Season awards as the side were crowned Danish champions.
[6] Following his form at youth level Duelund was promoted to the first-team, making his league debut in March 2015 against Hobro IK, coming on as a second-half substitute for Petter Andersson.
[11] He made his debut for the club on 16 September in a 1–1 away draw against Zorya Luhansk, coming on as a substitute in the 59th minute for Volodymyr Shepelyev.
[18] On 22 June 2021, recently promoted Dutch Eredivisie club NEC Nijmegen announced that they had signed Duelund on a one-season loan from Dynamo Kyiv with an option to buy.
[22] He started the 2022–23 season in convincing fashion, scoring once and adding two assists on the second matchday in a 4–1 victory against FC Volendam.
[7] He featured twice at the tournament, including a start in a 3–0 loss to eventual champions Germany, before Denmark were eliminated during the group stages.