The 22-year-old flanker will make the switch from Leicester, although he has spent the past two seasons on a dual registration deal at Nottingham.
And having agreed a two-year deal at Headingley, Hemingway believes Leeds can bounce back to the Premiership at the first attempt.
He said: "I am really pleased to be joining Leeds Carnegie and I am excited about the potential we have here.
"It was a big decision for me to move away from Leicester having been part of the system there all my professional career but the vision here at Leeds Carnegie is something that I really want to buy into and I am looking forward to a fresh start here and the chance to get some game time under my belt next season.
"From my time at Nottingham, I know it is going to be a tough for us this season but the squad that Diccon Edwards is assembling looks to have a good balance to it and hopefully I can prove my worth during pre-season and stake a claim for the start of the season."
Hemingway follows Joe Ford (Northampton) and Stevie McColl (Doncaster) in joining Leeds.
Gilbert has released a new line of rugby cleats. The Gilbert Virtuo 8S is part of the exciting new product. Check it out.
The entire All Blacks apparel line has been updated for 2013/14. Check out the New Zealand All Blacks polo.
The Nike Tiempo is a solid rugby cleat and one of few styles still made from full-grain natural leather.
The Gilbert Blitz 8S rugby cleat is a great cleat at a great price of $69.99. Get a new pair of cleats today.
A cool looking all black rugby cleat with the high performance adidas is known for. Get in the Gear!
Wear the crest of the British and Irish Lions on your t-shirt. A great look for the summer.
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The New Zealand All Blacks training jersey for 2013/14. Get in the Gear!
The USA Rugby Pro Alternate rugby jersey is perfect for any fan of the Eagles. Get yours to wear during the summer Test matches.
The NEW All Blacks 2013/14 jersey has arrived at World Rugby Shop. Dare to wear the colors of the All Blacks.