Playing as an opener, the hard-hitting left-hander blasted 79 off 49 balls and also took three catches as the PM's XI chased down Sri Lanka's 8/131 with one ball and one wicket to spare at Manuka Oval.
Nielsen hit 10 boundaries in an impressive innings which marked his first T20 half-century and his highest score in the format.
Harry Nielsen heating up for #BBL09 😏
%E2%80%94 Adelaide Strikers (@StrikersBBL) October 24, 2019
🔟 boundaries in a career-best knock of 79 in the PM’s XI win tonight! 👌 #BlueEnergy pic.twitter.com/yUaRyPaILd
The 24-year-old, who recently signed a two-year deal with the Strikers, was rewarded with Player of the Match honours in a team stacked with international talent including T20 star Chris Lynn, Melbourne Renegades Championship player Dan Christian and Adelaide Strikers teammate Peter Siddle.
"I couldn't quite get the job done but it was nice to get a few runs," said Nielsen, who was dismissed with nine runs still required and five balls remaining.
"I was just trying to take it as deep as possible. We kept losing wickets at probably the wrong time and their spinners bowled really well through the middle, I just tried to hit the gaps and run hard."
Sri Lanka begin a three-game T20I series against Australia this Sunday from 2pm at Adelaide Oval.
Strikers Alex Carey and Billy Stanlake are named in Australia’s 14-man squad and could feature in the series opener.
Tickets to the match are still available.