Madonna’s longtime publicist, Liz Rosenberg, a 39-year veteran of Warner Brothers Records, will leave the label to start her own firm at the end of February, the company announced on Tuesday. Some of the artists she works with at Warner Brothers, including Michael Bublé and Cher, will move with her to the new agency, Liz Rosenberg Media.

“We are delighted that as she begins her own enterprise, we will continue our association with her on behalf of several of our key artists,” Tom Whalley, the chief executive of Warner Brothers Records, said in a statement. While Ms. Rosenberg has worked with many prominent artists, no one has required as much attention – or received as much attention — as Madonna, who was an unknown performer when the two first met in 1983. Madonna left Warner Brothers for Live Nation in 2007, but Ms. Rosenberg has continued to represent her.