Mr Pither, who also steps down as a director, set up the company with chief executive Graham Forrest and led its expansion to overseeing 12 building services businesses.
A statement released by the company said: “Mr Pither is stepping down in order to avoid any potential future conflict of interest between his other business commitments and the activities of the group.”
Mr Forrest said: “Jon will be greatly missed by the board and, in particular, by me. Northern Bear's growth and success to date is due, in no small part, to his great experience and excellent advice.”
Howard Gold the deputy chairman will assume the role of chairman following Mr Pither's resignation.
At the beginning of October Northern Bear confirmed in a trading statement that turnover and profit before tax in the last six months was in line with market expectations despite the global economic downturn.
In response to the economic climate it has further tightened its acquisition criteria although it expects to continue its acquisitions strategy.
Businesses operated by Northern Bear include plumbing, heating and mechanical services company DJ McGough, asbestos speciaist Chirmarn, building contractor Hastie D Burton and refurbishment firm MGM Ltd.