The Boardwalk Empire star has appeared in four episodes of the NBC comedy as private eye Len Wosniak.
Buscemi will reprise the role in a new instalment, due to air on February 16, which he will also direct.
"After Jack (Alec Baldwin) gets mugged, he tries to reach out to his connections on the police force," series star Tina Fey told Entertainment Weekly.
"Jack wants Len to help him form a private police force where the salary starts at $5 million, so the police have the same interest in protecting the rich."
Emma Stone, Andy Samberg and Nick Cannon all recently signed up to play themselves in a forthcoming episode of 30 Rock.
Alec Baldwin has also signed on for a potential seventh season, despite rumours that the 53-year-old actor planned to exit the show.
30 Rock airs on Thursdays at 8/7c on NBC.
> 30 Rock star Tracy Morgan rushed to hospital from Sundance festival
Watch a clip from 30 Rock below: