Gaga is moving with Adrian Read to his new consultancy Inside/Out, joining other music clients including The Temper Trap and Best Coast.
Read is setting up the agency with Chloe Melick, who was most recently head of publicity at Sony RCA, as well as publicist for Jessie J and Kate Nash.
Read and Melick previously worked together at Polydor Records.
Inside/Out will focus on music, fashion and entertainment clients, providing publicity, social media, events and management support. Non-music launch clients include fashion enterprise SHOWstudio and youth development organisation Urban Development.
Read joined Darling Department in 2010 as head of press, and built a roster that included David Lynch, The Temper Trap and Fever Ray.