By SABC Sport
24th December 2022
The 49-year-old Dane was appointed to the top job in 2018 and guided the club into the Premier League for the first time in their history in 2020/21, ultimately finishing 13th in their top-flight campaign.
Frank's side currently sit 10th and will return to Premier League action against Spurs on Boxing Day bolstered by a 2-1 win over reigning champions Manchester City before the World Cup break.
"Being a head coach at a club is like a relationship; there are highs and lows," said Frank.
"I have been here six years in total, which is a long time in modern football, and I'd like to say thank you to the fans for the support you give us - the players, the staff, everyone involved with the club.
"The warmth, support and kindness every time I meet a Bees fan has been amazing and it gives me extra energy to continue the work going forward.
"We attacked the Premier League in the first season and we're attacking it in our second season. I'm looking forward to hopefully continuing our progress and creating more magic moments together."
Frank first joined the Bees as assistant head coach in December 2016, and had already agreed to a new deal back in January that would have seen him remain at the club until 2025.
He is just the second man to lead Brentford in the top tier, and is tied with David Webb in third place for total wins as manager in club history (91).
Brentford, who have won four and drawn seven of their 15 league matches this season, are in a close battle for a top-10 finish and one of three sides on 19 points as the second half of the season kicks off.
They will first host Spurs on Monday before rounding out 2022 with a trip to West Ham.
Director of football Phil Giles added: "I'm sure I speak for everyone at Brentford when I say that I am very pleased that we have agreed this new contract with Thomas. It is well deserved following some excellent results and performances in the last 18 months.
"Thomas has a detailed knowledge of the game, but just as importantly is able to inspire the players and build strong relationships with our staff.
"He has proven himself to be a Premier League-level head coach but retains an open-mindedness to keep learning and improving himself.
"The recent addition of Claus Norgaard as an assistant first team coach, along with the opening of the Robert Rowan Performance Centre, gives Thomas, me and all the players and staff new energy to keep working hard and seeing how far we can take the club."