The actress, who plays Eva Price, was handed the deal after pleasing bosses with her performance on the ITV1 soap.
Tyldesley's character is apparently being lined up for an "explosive" new romance, possibly with Peter Barlow, played by Chris Gascoyne.
"Eva has gone from strength to strength, to everyone's delight," a Coronation Street source told the Sunday Mirror.
"We have big plans for Catherine towards the end of the year - she will be involved in some cracking storylines."
Tyldesley joined Coronation Street in June alongside Michelle Collins and John Michie as the Price family.
She recently defended Collins's much-discussed Northern accent, insisting that she "can't understand the fuss".
> Interview: Catherine Tyldesley (Eva Price, Corrie)