[1][2] In 2016, Olesen won the International Juniors of Belgium and was runner-up at the English Boys' Open Amateur Stroke Play Championship for the Carris Trophy, where he shot a final round of 62 and lost a playoff to Angus Flanagan.

[3] Olesen has represented the Danish National Team, including at the 2017 Junior Golf World Cup in Japan and the 2023 Eisenhower Trophy in Abu Dhabi.

He finished the season with a scoring average of 69.53 as the top-ranked junior college player according to GolfStat, and received the NJCAA Phil Mickelson Outstanding Freshman Award.

[6] In July 2024, Olesen made history by becoming the first Dane to win The Amateur Championship, triumphing, 4 and 3, against Dominic Clemons in the 36-hole final at Ballyliffin Golf Club in Ireland.

The victory earned him a spot in the 2024 Open Championship at Royal Troon, where he made the cut to finish tied 60th alongside Phil Mickelson and defending champion Brian Harman.