He has signed a three-and-a-half year contract at the DW Stadium, joining them from the Scottish Premier League side Kilmarnock.
"Conor is a young, hungry player we have been looking at for a while," the Wigan manager Roberto Martinez told the Latics' official website.
"He has developed in an incredible manner over the last six months and it's fortunate that we've been able to move for him before he has achieved his full potential, which we're hoping he will do in a Latics shirt. We are delighted to welcome him on board."
The Iron had agreed a fee with Killie for the striker, but after holding talks with manager Ian Baraclough the player turned down a move to North Lincolnshire.
Derby County had a £425,000 bid rejected earlier on Monday, with Wigan stepping in and completing the capture shortly before the deadline.
"It was a big decision to leave a club that has been so good for my career but I'm a Wigan Athletic player now and I want to prove to everyone here they've made the right choice, and prove myself in the Premier League," added Sammon.