The Tony nominee has starred on two 30 Rock episodes in previous seasons as Liz Lemon's (Tina Fey) wholesome mother Margaret.
In an interview with Broadway World, Gillette revealed that viewers should expect her to be back on 30 Rock before the series wraps.
"[30 Rock producer] Don Scardino told me we all are going to be in the finale, but that's all I know right now," the actress said.
She added: "[Don] told me that a few weeks ago, so we'll see what happens - I don't want to bother Tina, she is busy enough as it is!"
It is not yet known if Buck Henry - who plays Liz Lemon's father Dick Lemon - will reprise his role this season as well.
30 Rock executive producer Robert Carlock previously expressed hopes that Michael Sheen and Will Arnett would make guest appearances in the final episodes.
The show returns on October 4 at 8/7c on NBC.
Watch Anita Gillette in a clip from 30 Rock below: