Guy Oseary, who partners with Madonna in Maverick Records and Maverick Films, will moonlight as a manager.

Oseary will become a principal in Untitled Entertainment, the management shingle run by Jason Weinberg and Stephanie Simon, which has a close association with Gotham-based management shingle Parseghian Planco.

Weinberg and Oseary confirmed the latter will be joining the company as a principal player, though both said Oseary will remain committed to Maverick’s music and movie ventures.

Madonna, Oseary and Ronnie Dashev own 60% of Maverick Records, with Warner Bros. owning the rest. The record company has been in the news recently as the Maverick partners are in a legal spat with WB over dissolution of that partnership, which runs out later this year.

Oseary, 31, became a music manager at 16. He joined Madonna’s upstart label when he was 17. He was a full partner by age 23 and began the film division two years ago.

Maverick Records artists include Alanis Morisette, Michelle Branch and the Deftones. Maverick Films projects include the DreamWorks pic “My Sassy Girl,” a pic which will be directed by Gurinder Chadha.

Oseary is also exec producer of the Carson Daly NBC talker “Last Call,” and he is exec producing a miniseries at NBC about the 1980s. He also recently completed a book called “On the Record,” featuring interviews with the likes of Bono and James Brown, each of whom answer the same dozen questions.

Given that full plate, Oseary’s decision to become a manager again seems a surprise. Madonna will not be involved in his management venture. Weinberg said his value will be bringing in new clients plus helping the management company expand in the branding game and other areas.

“I’ve known Jason since I first started out, I’ve watched his company grow, and I’ve admired its integrity and class,” Oseary said.

Said Weinberg: We believe in Guy, and he will add a lot of value to other clients who are already being properly serviced.”

A partial list of Untitled’s clients include Asthon Kutcher, Naomi Watts, Hilary Swank, Peter O’Toole, Joseph Fiennes and Laura Dern.