The 24-year-old Dane took a three shot lead into the final round ahead of Frenchman Victor Dubuisson, holding on to win the tournament with a total of 17-under 271.
Olesen admitted to not playing his best golf of the tournament, saying he found himself quite emotional on the final day.
‘I didn’t play my best golf these two days, and to keep fighting out there and keep believing in myself, I’m very proud of what I did there,’ Olesen said.
Get in front of tomorrow's news for FREE
Journalism for the curious Australian across politics, business, culture and opinion.
READ NOWOlesen fired a final round of one under 71, including three bogeys, more than in his first three rounds combined.
Olesen had a comfortable three shot lead by the 18th, and said he was able to enjoy the atmosphere of the tournament.
‘When I hit my tee shot on 18, that’s where I felt like ‘now I pretty much got it’,’ Olesen said.
‘I hit a great second shot in there and then gave my caddie the fist pump; it was a good walk up 18.’
Playing five groups behind Olesen, Dubuisson provided the champion with his greatest challenge.
The Frenchman said he was extremely happy with his long game but let himself down at times on the green.
‘You never know what can happen in the last round. Guys playing in the last groups, they don’t play the same way that I played today,’ Dubuisson said.
Played for $1.75million (AUS), the ISPS HANDA Perth International is Australia’s richest professional golf tournament and the only co-sanctioned by the PGA Tour of Australasia and the European Tour.