The reigning premier has agreed to pass on picks No. 19 and 40 to the Giants for O'Rourke, but will also receive pick 43 back from GWS.
O'Rourke was the No. 2 pick in the 2012 NAB AFL Draft, but played just nine games in his two season with the Giants as he battled hamstring and back issues and a broken jaw.
As a junior with the Calder Cannons, O'Rourke was a skilled midfielder with good pace, who could win the ball at stoppages and spread hard into open space.
The Giants now hold picks No.4, 19 and 21 in next month's draft.
Hawthorn list manager Graham Wright said on Thursday the club was excited to secure O'Rourke.
"Even though Jonathan has been interrupted with injury, he has shown some real promise in his first two seasons with the Giants," Wright said.
"Jonathan is a versatile midfielder with excellent ball use, can play inside and out and has a good combination of speed and endurance.
"We're very confident he will develop into an important part of our team in the future," he said.
Hawthorn list manager Graham Wright said on Thursday the club was excited to secure O'Rourke.
"Even though Jonathan has been interrupted with injury, he has shown some real promise in his first two seasons with the Giants," Wright said.
. @traderadio and @HawthornFC fans - Jono O'Rourke numbers outside the AFL pic.twitter.com/LjT488fB08
— Champion Data AFL (@championdata) October 9, 2014
"Jonathan is a versatile midfielder with excellent ball use, can play inside and out and has a good combination of speed and endurance.
"We're very confident he will develop into an important part of our team in the future," he said.
GWS list manager Stephen Silvagni said: "We think this is a best possible deal under the circumstances which gives us a first round selection at next month's draft that we could also trade."
