The European champions completed the signing of the highly-rated versatile midfielder from Barcelona on a four-year contract for an initial fee of 20million euros (£17.3m), with add-ons taking the total amount to 25m euros (£21.6m).
After arriving in Munich this afternoon, the 22-year-old was quick to hail the significance of Guardiola at Munich, having worked under his fellow Spaniard when they were both at the Nou Camp.
When asked why he chose Bayern, Thiago told the club's official website: "On the one hand, there's the history of the club, which has been one of the best in the world for many years. On top of that, this team plays very attractive football. And I believe the arrival of Pep Guardiola will provide an additional boost.
"We've known each other for a long time and he's a coach who has placed great faith in me. I'm a huge fan of the way he likes football to be played.
"There aren't many coaches in the world with his ability. He was definitely one of the important reasons for me making the move to Munich."
Guardiola last week pinpointed Thiago as his number one transfer target in his first summer with Bayern and club chairman Karl-Heinz Rummenigge was delighted to appease his new coach.
"We're delighted we've successfully negotiated this major transfer," said Rummenigge.
"Only recently, Thiago was named best player at the Under-21 European Championship. He's a fantastic player with huge potential, and he will make FC Bayern stronger."
Thiago came to the fore in Spain's triumphant Under-21s European Championship campaign in Israel with a string of impressive performances, most notably when he scored a hat-trick in the final against Italy.
He becomes the fourth member of that victorious squad to make a big-money move this summer, following Real Madrid's signings of Isco, Asier Illarramendi and Dani Carvajal.
"I'm really looking forward to it and I'm extremely happy. If there's a day in your life when you can be completely happy, today is one of those days. I'm thrilled to be at a massive club like Bayern Munich," he said.
Thiago was heavily linked with a move to Manchester United, who have quickly switched focus to his now former Barcelona team-mate Cesc Fabregas, but the Italian-born star is relishing the chance to settle down in Bavaria.
"Munich is a spectacular city with fantastic flair and a tremendous passion for football. I'm really enthusiastic about this adventure. I hope I play plenty of games, and that we can retain the trophies from last season," he added.