The Warriors have signed the scrum half immediately due to their injury problems. They will pay Salford an undisclosed fee for the development of the player. Smith was out-of-contract at the end of the season with Salford.
Smith has agreed a three and a half year deal at the DW Stadium keeping him there until the end of 2015, and is looking to win some silverware which he believes would otherwise elude him at Salford.
He said: “This is a fantastic move for me and a wonderful opportunity. Wigan are a great club with some excellent players and I am looking forward to hopefully playing my part in bringing more success in the months and years to come.”
Wigan coach Shaun Wane admitted he had been an admirer of Smith, and looked forward to working with the 24 year-old.
Wane said: “We are delighted to have secured his services and he is an excellent addition to our squad.
From my early discussions with him, I knew that my coaching team could do things with him. He is very vocal and plays very directly and he will fit into our system with ease.”
Smith will wear the number 38 on the back of his shirt for the Warriors.