Mitrovic first joined the Cottagers on a short-team deal in February 2018, and quickly became a cult hero among fans for his goalscoring exploits.
And he will now line up at Craven Cottage on a permanent basis after Fulham announced the transfer on Monday, in a deal believed to be worth £22 million ($29m).
"Mitro's back - and he's here to stay", the club stated on Twitter.
Fulham added in a statement: "We are delighted to confirm Aleksandar Mitrović’s return on a permanent deal for an undisclosed fee from Newcastle United.
"The popular striker has signed a five-year deal, keeping him at Craven Cottage until at least the summer of 2023, and will wear the number nine shirt."
"Mitrovic originally joined the Whites on loan at the 11th hour on deadline day in January, and went on to have a hugely significant impact in our promotion to the Premier League.
"The 23-year-old striker proved to be the perfect fit for Fulham, scoring 12 times in just 17 starts to help the team reach Wembley.
"Instantly taken to by the fans, the sounds of the 39,000-strong White Wall belting out “Mitro’s On Fire” during the celebrations at the national stadium will live long in the memory.
"Such was his popularity, he came fifth in the voting for Fulham’s Player of the Season award, despite spending less than half the campaign in SW6."
Speaking after putting pen to paper on a five-year deal, Mitrovic also expressed his delight at returning to the club.
"I’m very glad and happy and proud to finally be here and officially become a Fulham player. I’m happy to the moon and back," he told Fulham's official website.
"I have love for the fans. They’re amazing fans and I have a really good connection with them.
"This is a big club and last year we made history, we did big things, and I want to continue this. We want to keep making big things, and with all the fans behind us I think we can go far."