Unsworth, 33 moves to the JJB Stadium after 16 months service at Bramall Lane, during which time he made no fewer than 39 (+ 1 as a sub) games whilst scoring dour goals which included the one on his debut at home to Coventry City (W 2-1).
Unsworth said: "I'm delighted to sign for Paul Jewell and Wigan. They're a club with great ambition and I hope to be able to play some part in their story. I know how tough the Premiership can be, and hopefully, I can use that experience to benefit the club."
"I know Kevin Kilbane and Matt Jackson very well, and the atmosphere among the lads seems to be excellent. I'm looking forward to the challenge ahead!"
Meanwhile Leeds United signed former Chelsea and Glasgow Rangers striker Tore Andre Flo on the 3 January. Although he didn't play for the Blades he was on trial at Bramall Lane during the early 1990's.
United opted not to sign Flo but did sign his brother, Jostein who had a successful career in England. Tore Andre signs for the Whites for £6,000 a week plus £1,000 a goal bonus. It is hoped that the former Norwegian international will keep the Elland Road club in the Championship.
Elsewhere former Sheffield United Midfielder George Santos left Brighton & Hove Albion to join Conference League leaders Oxford United on loan yesterday.