Putin has ruled Russia since 2000. The new, now six-year term will keep him in power until 2018 with the option of running for a fourth term.
After taking the oath of office, Putin stated his commitment to democracy.
"I consider service to the fatherland and our nation to be the meaning of my life," Putin said to 3,000 guests.
Outside the ceremony, riot police worked to prevent at least 1,000 demonstrators from protesting Putin's re-election. A total of 120 people were detained, including opposition leader Boris Nemtsov.
The Associated Press contributed to this report.
