Tate, who made a guest appearance at the end of the last series of the sitcom, will reprise her role as Nellie Bertram, a misguided special projects manager.
Her character will return halfway through the current series of the show, which is currently airing on NBC in the US.
"Catherine is hysterical," said executive producer Paul Lieberstein.
"We introduced her briefly in last season's finale and knew she had to be a part of the show somehow. We're thrilled that she's joining the cast."
(Source: BBC News)