A number of clubs from around Europe were interested in recruiting the 27-year-old, who has had previous stints at Border Reivers and London Irish.
However the Scotland A international has been sold on the ambitions at the Memorial Stadium by coach Liam Middleton.
"I'm delighted to be moving to such an ambitious club," he said. "I met with Liam and I am excited about my future at the Memorial Stadium.
"There was interest from other clubs but I was really impressed with the vision of Bristol Rugby and the environment that has been built here.
"I look forward to joining up with the squad and helping Bristol move forward next season."
Bristol, who are through to the RFU Championship play-off semi-finals, have also agreed deals with Bruce Douglas (Worcester), Adrian Jarvis (London Irish) and David McIlwaine (Doncaster).
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.