Tuilagi, who has also spent time in the Premiership at Leicester, negotiated a release from his final year of his deal at the Sharks earlier in June.
And the powerhouse Samoa international will now to team up with his former team-mate Darren Edwards at Rodney Parade.
Tuilagi, who can also play on the wing, spent two seasons at Leeds with Edwards between 2006 and 2008 before both players left Headingley.
Tuilagi, now 25, subsequently made the move to Sale, while Edwards retired to begin coaching, with the much-travelled scrum-half replacing Paul Turner at the helm of the Dragons this year.
Edwards has highlighted Tuilagi as the man to add some steel and experience to his back division.
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.