The 27-year-old joined the Clarets ahead of the 2022-23 term from Anderlecht, linking up with Vincent Kompany as the Belgian took on his first management role in English football.
Cullen enjoyed a stellar campaign for the Championship-winning Clarets, playing 43 second-tier matches in a side which broke the 100-point mark as they cantered to first place.
The Irishman's performances in the Burnley engine room were enough to see him earn individual accolades, with the midfielder winning the club's Player of the Year award ahead of the likes of Ian Maatsen and Nathan Tella.
Kompany's Clarets have now announced that Cullen has put pen to paper on fresh terms at the Premier League newcomers, meaning his terms in Lancashire now run until 2026.
"I am really happy to extend my time here, especially off the back of last year which was a really successful year for the club. I cannot wait to continue my career with Burnley, " Cullen told the club's official website.
"It will be great to get back to Turf Moor this weekend and be in front of the fans again and hopefully get our first three points on the board."
Europa Conference League-bound Aston Villa are the visitors to Turf Moor on Sunday afternoon as Burnley aim to collect their maiden points of the new season following a 3-0 loss to Manchester City on the opening night.
The Clarets' scheduled fixture at Kenilworth Road against Luton Town was postponed due to the Hatters' home not being ready to host a top-flight fixture, allowing Kompany more time to work with his squad ahead of the clash with Unai Emery's side.
Cullen is the third Burnley man to sign a new long-term deal the club this summer, with Anass Zaroury and Manuel Benson also extending their stays following successful terms in the second tier.
The Championship winners have also brought in a raft of new faces as they aim to avoid an immediate return to the Football League, with the likes of Luca Koleosho and Jacob Bruun Larsen from Espanyol and Hoffenheim respectively.