The British rocker passed away at a hospital in Toronto, Canada on Wednesday (30Sep15) following a long illness.
His age had not been released as WENN went to press.
The remaining members of the folk band announced the news in a post on their website.
It reads: "It is with great sadness that we have to tell you that our dear friend and colleague Simon Cowe has died yesterday, 30th September. Simon had been ill for some time, and was being cared for in hospital in Toronto, a city he had made his home since the early nineties. At the moment we don't have the words to express how we feel. Our thoughts are with his children Jessie, Dylan, and Bernadette."
Cowe co-founded the group in the 1960s, and the five-piece enjoyed chart success and international tours.
Their second album Fog on the Tyne became the biggest-selling album in the U.K. of 1972.
The band, which went through many line-up changes, split in 1973 and reunited in 1978.
Cowe left in the early 1990s and moved to Canada to set up a microbrewery business.