The German’s appointment was confirmed on Tuesday as he was named the successor to Frank Lampard, who was sacked on Monday.
The club said Tuchel had signed an 18-month contract “with the possibility of an extension”.
Tuchel also took charge of his first training session on Tuesday evening and is expected to be in the Stamford Bridge dugout for Wednesday’s Premier League clash with Wolves.
“I would like to thank Chelsea FC for their confidence in me and my staff,” Tuchel told the club website.
“We all have the greatest respect for Frank Lampard’s work and the legacy he created at Chelsea. At the same time, I cannot wait to meet my new team and compete in the most exciting league in football.
“I am grateful to now be part of the Chelsea family – it feels amazing!”
Chelsea director Marina Granovskaia added: “It is never easy to change head coach in the middle of the season but we are very happy to secure one of Europe’s best coaches in Thomas Tuchel.
“There is still much to play for and much to achieve, this season and beyond. We welcome Thomas to the club.”
Lampard did his bit as a Chelsea player, becoming the club’s all-time leading goalscorer, and as a manager too. He steered the Blues to the FA Cup final last season and secured qualification for the Champions League in what was deemed a largely successful first campaign in charge at Stamford Bridge.
However, after spending more than £200m on new players in the summer, Chelsea finds themselves in midtable in the Premier League and in danger of missing out on qualification for next season’s Champions League.