The 29-year-old, who left Tayside in 2006 after moving to Celtic in a £500,000 deal, has rejoined his old club following his release by Bristol City.
Wilson said: "Tannadice holds great memories for me as I had great times here as a young player. I am coming back as an older, more experienced footballer. I know I can be a useful asset for Dundee United and I cannot wait to get playing again.
"I hope this deal leads to a longer-term deal as there is no doubt I play my best football when I am settled. I am joining a young squad with some experienced players but I can help add experience. Every successful team has that mix of youth and experience and I see real potential here."
Wilson made his United debut as a 17-year-old in a 1-0 victory over city rivals Dundee in January 2002 and went on to play 138 times for the club.
He left for Parkhead four years after making his first-team bow, where he won four Scottish Premier League crowns with the Hoops.
The 29-year-old quit Celtic Park last summer to move to Bristol City but started just eight games for the Robins and becomes Arabs boss Jackie McNamara's 10th signing of the new campaign.
The Tannadice manager added: "Mark brings experience and ability to the squad. The short-term deal will give him an opportunity to show there are no fitness concerns.
"He will enhance our squad and his versatility is important. He is comfortable at right-back and left-back and also gives the option of playing in front of the back four. He is the type of player who will help us get control of the ball and settle us down when required and I am delighted he has signed."