The agreement sees MBC co-managing director Barbara Charone take over Wainwright's representation from the end of this year, following the expiration of the singer's current contract with MCT's Barry Taylor and Paula Quijano.
The highly-respected PR company will also continue to look after Wainwright's press - a role it has undertaken for seven years - and Charone says she is extremely excited about the new direction.
"It is no secret Rufus is my favourite artist of everyone I work with," she says. "I think he is a genius and I am keen to replicate the success he has had in the UK elsewhere in the world."
This, she explains, will see MBC pushing to win Wainwright extra radio airplay as well as syncs in television and film.
"It would also be great to get one of his songs covered on a TV talent show like X Factor - something like that would really bring him into the mainstream where he belongs," she adds, explaining her goal is to build on Rufus' existing fanbase in the US and to change the singer's perception in the media in time for the launch of his next album, which is predicted for release in 2012.
"I don't want people thinking Rufus' music is a big secret. I want his songs to be covered by other artists and for his reputation to grow, so by the time his album is released it has the potential to be very commercial," she explains, adding part of her role as manager will involve taking Wainwright's opera Prima Donna to the US.
In taking on management, MBC joins a growing trend: PR company Darling Department represents Filthy Dukes, Joe Worricker and Totally Enormous Extinct Dinosaurs, for example, while Republic Media director Sue Harris manages Sparks.
However, Charone stresses her new management role will just be a "one-off" and that she will retain her position as MBC managing director as well as all press duties for the company. She adds she was inspired to pick up the mantle after Wainwright approached her for manager recommendations.
"The more I thought about it, the more I thought no one would be good enough," she notes. "Rufus is not your typical artist - and a stereotypical manager who represents a number of acts is not going to be able to offer him the attention he deserves. Unlike many other artists, he is not interchangeable. His manager needs to know about his music, his background, the way he works - someone who is more of a fan than a manager."