Wigan took the lead 10 minutes in as Thomas Leuluai crashed over to put the Warriors 6-0 up.
Seven minutes later, Wigan's Michael McIlorum was given a red card for a late hit on Anthony Laffranchi, which made it difficult for the Warriors to defend their six-point lead.
Pat Richards levelled the scores three minutes into the second half but the Saints once again responded with three more tries. Andy Dixon broke the line for the Saints' first, with Josh Jones and Jonny Lomax adding the others.
At 26-12 with two minutes remaining the victory was effectively sealed but Wigan added a late consolation try through Sam Tomkins to leave the final score at 18-26.