The New Zealander has experience with Auckland, ACT Brumbies, and, most recently, French side USON Nevers.
Whetton, 24, made five appearances for Leicester in 2014-15 and returns to England now to aid Carnegie’s promotion bid from the Championship next season.
His father captained New Zealand 15 times in 58 Tests and was part of the 1987 World Cup winning squad as was his uncle - the flanker Alan Whetton.
With ex-England lock Chris Jones having announced his retirement last month, the club has needed to strengthen in that area.
Carnegie coach Bryan Redpath said: “I am delighted to get Jack on board as a line-out caller and someone who can play in the back-row as well.
“His high work-rate, ball-carrying and aggressive nature are big assets to us going forward.
“I am looking forward to working with Jack for the next two seasons.”
Whetton added: “I’m very excited to be joining Yorkshire Carnegie next season.
“It is a famous club, rich with history and culture, which I can’t wait to be a part of.
“I am really excited about the challenge of being promoted and am willing to do everything possible to get there.”
Meanwhile, Johnny Sexton has been ruled out of Ireland’s tour of South Africa.
The 30-year-old Leinster fly-half suffered a shoulder injury during Saturday’s 20-10 Pro12 final defeat by Connacht and needed minor surgery.
Coach Joe Schmidt has also lost Luke Fitzgerald and Dave Kearney to injuries sustained at Murrayfield, and in a further blow Rob Kearney pulled up in training on Wednesday with a hamstring strain which will rule him out of the tour.
Ireland have called up Craig Gilroy, Matt Healy, Ian Madigan and the uncapped Tiernan O’Halloran as replacements.
The squad are due to depart on Sunday and will play Tests in Cape Town, Johannesburg and Port Elizabeth on their first tour of South Africa since 2004.