The actress, who played Sharon Theodopolopoudos for nine years, also made a guest appearance in ITV cop drama The Bill last September.
A spokeswoman for the show told DS: "We are thrilled that Pauline will be part of an upcoming episode of Casualty.
"Pauline will be playing a homeless person who ends up getting trapped within an internet cafe and suffers horrific injuries."
The dramatic scenes will be shown in mid-October when Casualty enters its 20th anniversary year.
Soap Scoop
Home and Away relationship twists - PicsWe take an in-pictures look at next week's Home and Away episodes.
Soaps Interviews
Emmerdale star talks John death aftermathWe chat to Emmerdale's Adam Thomas about John's death and more.
Soap Ratings
'Emmerdale' John, Moira plot takes 7.7mEmmerdale continues to perform strongly on Wednesday evening.
Reality Bites
'Big Fat Gypsy Weddings' returns: ReviewReality Bites's verdict on the return of Big Fat Gypsy Weddings.
