The Brazilian, who is believed to have cost Spurs around £17m, said that he is "very happy and excited" to sign for the Premier League club.
"I am very happy and excited to have joined Spurs. It's a huge pleasure for my career to be at a club as big as Tottenham," he wrote on Twitter.
Paulinho, who has become Andre Villas-Boas's first summer signing, completed his medical at White Hart Lane on Friday before penning a contract.
Spurs start the new season at Crystal Palace on August 17.