Thomas Frank said on Friday he had "left a big piece of my heart" at Brentford after taking on the daunting task of reviving Tottenham's Premier League fortunes.
Spurs announced the Dane as their new head coach on a three-year deal on Thursday, as a replacement for the sacked Ange Postecoglou.
Frank, 51, won 136 of his 317 matches across a seven-year spell at Brentford, taking them into the Premier League in 2021.
In an emotional message posted on Brentford's website Frank said: "The time has come for me to move on. But, even as I leave, I know I have left a big piece of my heart at Brentford, not just at the football club but with the community and, of course, the incredible and loyal supporters.
"I want to extend my profound gratitude to the club for giving me the chance to pursue my dreams and for everyone involved who made the journey such a memorable one."
He said it had been a privilege to be allowed to be part of such a "special community".
"Whatever we have achieved, we have achieved together, and our success is built on unity, spirit, courage and ambition at every level of the club and among the fans," he said.
"Everybody has contributed, and every contribution has been invaluable. I am not just leaving a football club, I am saying goodbye to friends whose support through good and bad times I will carry with me always."
Frank, who becomes Tottenham's fourth permanent boss since 2021, is tasked with lifting the club back among the Premier League's elite.
We are delighted to announce the appointment of Thomas Frank as our new Head Coach on a contract that runs until 2028.
— Tottenham Hotspur (@SpursOfficial) June 12, 2025
Welcome, Thomas! 🤍
Spurs will play in the Champions League next season thanks to their Europa League success in Bilbao, where they beat Manchester United 1-0 in the final.
Their 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 in which Tottenham finished 17th after losing 22 of their 38 games.
Tottenham finished seven places and 18 points below Frank's Brentford.