Fletcher, who was Newcastle's chairman during the '90s, lost his battle with cancer last night.
The Scot was instrumental in bringing big names to the club during his spell as chief executive, overseeing a golden period that almost saw them clinch the Premier League title under Kevin Keegan.
"Newcastle United were very saddened to hear the news of the death of former chief executive Freddie Fletcher after a brave fight against cancer," said a club spokesman.
"Freddie did great things for the club in the 1990s, especially in the early days of the Premier League, and helped re-establish the club in the top echelons of English football.
"He had great enthusiasm, knowledge and football expertise and he also played a key role in bringing the likes of Alan Shearer, David Ginola and Faustino Asprilla to the club. Our thoughts in this time of sorrow are with his family."
The Magpies are expected to honour Fletcher in their match against Aston Villa on Sunday.