Target Media - which owns Organic and a number of other agencies - was acquired by Havas in October last year.
Organic North, which opened this month, will work with the agency's London headquarters to service existing clients, as well as offering "on-the-ground publicity services in Manchester and the surrounding areas", a company statement said.
Organic's roster of clients includes Disney, Lionsgate, and Twentieth Century Fox. The agency also handles UK publicity for Netflix Originals, The Regent Street Cinema, and German Films.
A spokeswoman for the agency added: "Having a presence in the North also puts us in a great position for handling campaigns with a regional focus and we are conveniently positioned for many media organisations, production companies and film and arts festivals."
Organic account manager Chris Boyd, who has relocated to Sheffield, will work from the new office. He joins a number of colleagues at Organic's sister agency Target Live in Havas Village, and will work alongside "entertainment PR associates" in the region, the statement added.
Boyd will report to Caragh Cook, who is MD of both Organic North and the London office. She said: "Having a home in Manchester means we can provide a communications hub for the North, situated in the heart of an exciting, progressive city."