Burstyn will star alongside Natasha Lyonne in the single-camera pilot, which is written and executive-produced by Poehler, Josh Bycel and Jonathan Fener and directed by David Wain.
"Old Soul" follows Nadia, a reformed wild child, played by Lyonne. Nadia cares for the elderly and feels she has more of a connection with her clients than she does people her own age. Burstyn will play Nadia's Aunt Eileen, who is a cancer surviver and an earthy lesbian with a New Age bent.
Burstyn, a Tony Award winner for Same Time, Next Year, has also starred onstage in Picnic, Oldest Living Confederate Widow Tells All and Shirley Valentine. The Academy Award winner's screen credits include "The Exorcist," "Alice Doesn't Live Here Anymore" and "Requiem for a Dream."