The actress will appear in five episodes of the Syfy drama's fourth season, TVLine reports.
Her character Charlotte Dupres is a new nemesis for the Warehouse team who is hiding a secret past.
English actress Walker is known for her roles on HBO's Rome and the BBC's Prisoners Wives, plus movies John Carter and Clash of the Titans.
The 46-year-old is also currently recurring on season five of CBS drama The Mentalist.
Warehouse 13 is currently on hiatus, with new episodes set to resume in April 2013.
Smallville actor Aaron Ashmore - who plays Steve Jinks - was made a series regular as of season four's third episode.
> Star Trek Brent Spiner joins Warehouse 13
> Being Human star Sam Huntington joins Warehouse 13
Watch a promo for Warehouse 13 below: