The former Chelsea boss says he has received a warm welcome in St. Petersburg and believes the club suits his ideas perfectly.
New Zenit coach Andre Villas-Boas said taking on the job was a no brainer due to the club's standing in European football.
Former Porto, Chelsea and Tottenham boss Villas-Boas was unveiled to the media on Thursday.
The Russian Premier League giant defeated Borussia Dortmund 2-1 in Germany on Wednesday but was still eliminated on aggregate 5-4.
It was a spirited display though, and Villas-Boas, who will be immediately tasked with winning the league, says it was an easy decision for him to make.
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"I've been very well received by all the people I've met in St. Petersburg," he told a news conference. "To be honest, there was no difficulty in taking this decision for me, because Zenit is a well-known club in Europe.
"The ideas that led to this decision suit my own ideas about football. This is an important step for me, that suits my ideas, and my career. Of course I knew a lot of Zenit's players before I came here. I'll learn more about them in the process of my work."
Villas-Boas confirmed that interim coach Sergey Semak would remain at the club as part of the first-team staff.
Zenit has won just one of its last seven league matches, form that saw former coach Luciano Spalletti sacked.
The club has dropped to second in the table but encouragingly, is just three points behind league leader Lokomotiv Moscow.
Spartak Moscow, Dinamo Moscow and CSKA Moscow are all within four points of Zenit though, meaning the race for the title will be hotly contested.
"If we win all nine remaining matches, Zenit will be champions," Villas-Boas added. "My goal is to bring Zenit to the top."
The 36-year-old also said he was pleased with the signs he saw from Zenit in Wednesday's triumph at Signal-Iduna Park.
"Last night's game was an excellent result for sure," he continued. "The main thing is that Zenit played as a team. I saw the team's spirit."