The British actress, whose credits include Doctor Who and Gulliver's Travels, will reprise her role as Nellie Bertram, one of the candidates who interviewed to replace Michael Scott (Steve Carell) at Dunder Mifflin last season.
Tate will appear through the second half of the season when Chairman of the Board Jo Bennett (Kathy Bates, who will not appear) hires Nellie as a special projects manager working for the corporate office.
"Catherine is hysterical. We introduced her briefly in last season's finale and knew she had to be a part of the show somehow," executive producer Paul Lieberstein said in a statement. "Her relationship with Robert California (James Spader) will be far from professional. We're thrilled that she's joining the cast."
The Office airs Thursdays at 9/8c on NBC.