The Magpies have been linked with a big-money move for the frontman, with reports suggesting they had already agreed a fee with Anderlecht.
However, general manager Herman van Holsbeeck has stressed that he won’t sell the Serbian this summer.
Van Holsbeeck said: “At 20, Mitrovic has scored 20 league goals this season.
“He scored against Arsenal, Dortmund and has also played for Serbia. This is a striker who you know can really improve a side.
“Therefore, we have decided against selling him. Mitro is aware and he wants to stay.”
Mitrovic bagged 27 goals this season for the Belgians, including Champions League strike against Arsenal, who have also been linked with the striker.
Newcastle are desperate to add to their strikeforce this summer, having struggled for goals all season.
Papiss Demba Cisse finished top scorer despite missing large chunks of the campaign through suspension and injury, while Emmanuele Riviere only netted once in the Premier League.
The Magpies are understood to be keen on QPR forward Charlie Austin and Burnley’s Danny Ings, though the latter has a number of suitors, including Liverpool.
Newcastle are also hoping to sign Ghana winger Andre Ayew, who is a free agent after leaving Marseille.