The former Under-21 international has made 30 appearances for Super Rugby side Stormers and joins countrymen Greg Goosen, Ashley Wells and Corne Uys at Kingston Park.
"He is a great player who is really well respected in South Africa and we've sealed another top notch second row - he is a tremendous athlete," said head coach Alan Tait.
"It now gives us more options in there and it will obviously increase competition. I'm sure the boys will be happy when they find out that he is joining the club."
The 28-year-old, who is due to arrive in England on Monday, said: "I am really looking forward to the challenge of playing for the Falcons.
"The Falcons are an ambitious club that wants to go places and I am really pleased to have the opportunity to move to Newcastle.
"I definitely want to be involved in something big at the club."
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.
The All Blacks Performance t-shirt is black with hints of blue from the training jersey. Very Cool.
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.