The change ends the previous arrangement, under which it was totally owned by Julia Reed, the company's managing director.
From now on, the shareholding will be split between Reed, the director Ringan Ledwidge, the head of production, Helen Williams, the senior producer Sally Humphries and Claire Neate, the executive producer of Battlecruiser, the company's music video division.
Reed created Harry Nash after buying a 90 per cent stake in the production company The End from Harmony Holdings in 1999. Reed said that she would have split the shareholding at the time of purchase, but was prevented from doing so under the terms of the deal.
In 2001, she bought the remaining 10 per cent of the company.
She claimed that the new structure would allow each of the partners to develop their own expertise and operate more effectively as a management team.
"Great companies are generally not just about the qualities of a sole leader," Reed said. "Harry Nash would not be where it is today without all of their, especially Ringan's, unwavering loyalty and commitment to the company and its creative profile."
Reed is a former chief executive of the production company Tony Kaye & Partners, where her task was to build the company while Kaye was shooting his first feature film, American History X.
Before that, she worked as an executive producer at Propaganda and later Satellite, where she was responsible for building up the commercial division.