He was due to play for the reserves in this afternoon's Pontins League clash at Hull City although a shortage of match fitness could mean his involvement in the senior squad being delayed a while longer.
Whalley became involved in a contractual wrangle with Cardiff at Easter and hasn't played a first team game since.
Latics took him on trial three weeks ago while the row was sorted out, and with a severance deal with the Bluebirds now agreed, he has signed a contract at Wigan until the end of the season.
No transfer fee is involved and the 29-year-old becomes Paul Jewell's fifth new recruit since the end of last term.
It's the second time Jewell has signed Whalley, previously buying him for Bradford from Crewe.
Jewell said: "Gareth will give us more experience in midfield.
"We're a bit short of bodies in there at the moment because of Jason Jarrett's injury and with one or two others out on loan.
"He's a quality footballer and is similar to Per Frandsen in many ways, just sitting in midfield and keeps things simple.
"Gareth was brought up at Crewe, knows the game well and has played at this level and above before.
"Unfortunately he hasn't played for a while so I would think it will be a couple of weeks before he is considered to start."
Whalley's fall-out with Cardiff occurred due to a clause in his contract which stated he was due a £50,000 bonus when he had played 23 league games last season.
When the Bluebirds fell out of play-off contention towards the end of the campaign, he was dropped one game short of that total.
Whalley watched from the stands last night as his new club were held to a goalless draw by Burnley.
It left Latics still unbeaten in second place, with Stoke taking over at the top after beating Ipswich.
The derby clash turned out to be a dour affair.
Jewell said: "It was a poor game. Burnley came for a draw and credit to them for getting that.
"We didn't have the craft to break them down, it's as simple as that.
"I can't remember either goalkeeper really having a save to make.
"If we have high aspirations, we are going to have to get used to teams coming here and making it difficult.
"I'm not going to be too hard on the players, and while I'm not happy, it just wasn't our night.
"We had most of the ball but didn't do enough with it to win the game.
"When we're at home, we have to create more chances than that.
"I thought we were the better team without really looking like breaking them down."
In contrast, Burnley manager Steve Cotterill was happy with the draw and admitted the Clarets had come to the JJB with a defensive game plan.
He said: "I felt Wigan's strength was down the spine of their team as Bullard and Frandsen are two good players in the middle, while everyone knows about Roberts and Ellington.
"My boys worked their socks off and we probably deserved our point for all that hard work."