Frank agreed a three-year contract with Tottenham and becomes the north London club’s fourth permanent boss since June 2021.
“We are delighted to announce the appointment of Thomas Frank as our new head coach on a contract that runs until 2028,” a Tottenham statement said.
“In Thomas we are appointing one of the most progressive and innovative head coaches within the game,” it added. “He has a proven track record in player and squad development and we look forward to him leading the team as we prepare for the season ahead.”
Tottenham set their sights on Frank after chairman Daniel Levy axed Postecoglou last week, just 16 days after he won the Europa League final against Manchester United to end the club’s 17-year trophy drought.
Frank is the 14th permanent manager of Levy’s 24-year tenure.
Levy made an official approach to Brentford earlier this week, with the deal concluded after Tottenham agreed to allow the Dane to hire his Bees assistant coach Justin Cochrane.
Frank’s Brentford contract was set to run until 2027, with a reported release clause of about £10 million (US$13.6 million).
The 51-year-old led Brentford back to the top flight in 2021 after an absence of 74 years and has established the west London club in the Premier League.
Now he will be tasked with lifting Tottenham back among the Premier League’s elite.
Tottenham will play in the Champions League next season thanks to their Europa League success in Bilbao, where they beat Manchester United 1-0.
Tottenham’s first European trophy for 41 years delivered on Postecoglou’s boast that he always wins silverware in his second season.
However, the Australian paid the price for a miserable Premier League season as Tottenham finished 17th after losing 22 of their 38 games.
Tottenham finished seven places and 18 points below Frank’s Brentford.
While Postecoglou was criticised for an overly-attacking game-plan for much of his two-season reign, Frank has been credited with a tactically flexible approach and a deft man-management style.
Frank will also bring head of performance Chris Haslam and first-team analyst Joe Newton with him from Brentford, while another assistant coach, Andreas Georgson, arrives from Manchester United.
Georgson spent a year at Brentford as a set-piece coach, while Tottenham’s technical director Johan Lange worked with Frank at Lyngby in Denmark.
Brentford director of football Phil Giles saluted Frank’s role in his club’s remarkable rise.
“From the moment he replaced Dean Smith, he understood what we were trying to build and his wisdom, coaching ability and emotional intelligence have helped transform the club,” Giles said.
“But it’s not just what you see on the pitch,” he added. “He forged a special connection with our fans, helped develop and improve players, and was instrumental in implementing the culture that has seen Brentford go from strength to strength.”
Frank began his coaching career in the youth set-up of the Danish national team before a three-year stint at Brondby.
He initially joined Brentford as an assistant coach before stepping to replace Dean Smith seven years ago.
After losing out in the 2020 Championship play-off final, Brentford bounced back to win promotion through the play-offs a year later.
Since then, the Bees have finished 13th, ninth, 16th and 10th despite consistently selling some of their best players.
Ipswich boss Kieran McKenna is the bookmakers’ favourite to replace Frank at Brentford.
Frank will manage Tottenham for the first time competitively on August 13 in the Uefa Super Cup against Champions League winners Paris Saint-Germain. (AFP)