The oath was administered at the Moi International Sport Centre Kasarani by Judiciary Chief Registrar Gladys Shollei and was witnessed by Chief Justice Willy Mutunga, Nairobi's Standard Digital Reporter reported.
The inauguration was attended by 11 heads of state and a variety of other international political players, including U.S. civil rights activist Jesse Jackson, CNN reported.
Kenyatta, the son of Kenya's first president, Mzee Jomo Kenyatta, won the election with 50.07 percent of the vote over Raila Odinga. Odinga is the son of Kenya's first vice president, Jaramogi Odinga, who was ousted from his role by Mzee Jomo Kenyatta after a series of disputes.
Raila Odinga offered his congratulations to the new president after his victory, leading some to hope the acceptance could help restore the African country's image as a place of stability, CNN reported.
Kenyatta took two oaths, one pledging allegiance to the Constitution, and the other a solemn affirmation of due execution of the office of president, Nairobi's Capital FM reported.