Viewers last saw the pub boss lifeless after a Redwater boat crash in June — while hubby Alfie seemed to have died during a brain op.
But actress Jessie Wallace, 46, will rejoin EastEnders early next year under returning boss John Yorke — who brought her Slater clan to the soap in 2000.
An insider said: “John loves the Slaters.
"A lot of people thought he might bring some of them back.
“He believes they’re long-standing favourites who should be at the heart of the show and thinks Kat’s return will be a hit.
“Nobody knew if she or Alfie would return so it looked like they had been killed.
"This will surprise fans.”
Jessie was on the BBC1 show from 2000-05 and 2010-16.
Fans watched loudmouth Kat have two flings, see her tot stolen in a baby-swap and suffer a miscarriage.
She and Shane Richie, 53, who plays Alfie, left in 2016 to find her long-lost son in Ireland — a plot covered in Redwater.
Executive producer John returned to EastEnders last month.