Souths agreed to release Simpson from the final year of his contract and he has penned a three year deal with the Giants.
“I am very excited and appreciate the opportunity to continue my football career over in England. I have always wanted to play overseas and to do it while I am still young would be a great experience,” he told the club’s website.
“I have enjoyed my time with South’s over the past four years and am very grateful for their major input in my career, and without them would not have the opportunity to join the Giants.
“Over the next three years I hope I can enjoy success and happiness with the Giants and can’t wait to meet the team and all the fans.”
The Queensland-born wing or centre made his NRL debut for the Rabbitohs in 2008 and played in 37 first grade matches.
Huddersfield managing director Richard Thewlis said that the club were pleased to have captured Simpson.
“We are very grateful to the Souths club for their assistance in securing Jamie a year earlier than perhaps we had anticipated,” he said.
The Giants are unsure if Simpson will be granted a visa in time for the start of the season but said that the player would continue to train with the Rabbitohs to maintain his fitness.