The 21-year-old joins from MLS expansion franchise Charlotte FC.
McGree was transferred to Charlotte FC from Adelaide United.
With Charlotte FC entering the MLS in 2022, Blues came to an agreement to take McGree on loan for the season.
Capped at Under-17 and Under-23 level, McGree is one of Australia's rising stars and earned a call up to the senior side for the first time three years ago.
He has just come off the back of a standout season with hometown club Adelaide in the A-League, scoring 13 times in 26 appearances. McGree also netted in Adelaide's 4-0 FFA Cup win over Melbourne City.
Adelaide signed McGree from Club Brugge in July 2019
McGree made his A-League debut for Adelaide in 2015/16 and joined the Belgians in 2017.
He was loaned back to the A-League and Newcastle Jets and Melbourne City before Adelaide took the plunge to splash out and secure him on a permanent basis.
McGree shot to worldwide prominence after joining Newcastle in January 2018 by scoring with an amazing scorpion kick in the A-League semi-final against Melbourne City.
The incredible goal was nominated for the FIFA Puskas Award for 2018.
There has been significant interest in McGree this close season with clubs from Turkey, Germany and Scotland reportedly keen.
But McGree opted to leave Adelaide to be part of the Charlotte FC adventure; they are backed by billionaire Carolina Panthers owner David Tepper.
His loan to Blues expires on 30 June, 2021.