She was administered the oath of office by Chief Justice of India K G Balakrishnan at a function in the Central Hall of Parliament House.
The function was attended by a host of VVIPs, including outgoing President A P J Abdul Kalam, Prime Minister Manmohan Singh, Lok Sabha Speaker Somnath Chatterjee, Rajya Sabha Deputy Chairman K Rahman Khan, UPA chairperson Sonia Gandhi, Union ministers, former prime minister Atal Bihari Vajpayee, opposition leaders, governors, chief ministers and members of the diplomatic corps.
A 21-gun salute was accorded to Patil after she was sworn-in as the country's 13th President.
She solemnly affirmed by the oath, which she took in English.
Bhairon Singh Shekhawat, who resigned as vice-president after his defeat by Patil in the presidential election, and leaders of the opposition in Lok Sabha and Rajya Sabha -- L K Advani and Jaswant Singh respectively -- too attended the swearing-in ceremony.
Patil's family members and kin were also present in the Central Hall of Parliament House.
In her address shortly after taking oath as President, Patil described herself as the republic's "first servant" and said her sincere endeavour would be to live up to the high expectations of the people who elected her to the top post.
She was given a "national salute" by the President's Bodyguards.
Earlier, setting in motion a series of ceremonial drills before the swearing-in ceremony, the Military Secretary to the President, Maj Gen Vinod Chopra, went to Patil's 9 South Avenue residence and invited her and her husband to the Rashtrapati Bhavan.
After the Presidential Bodyguards gave a national salute to Kalam, the outgoing President accompanied Patil to Parliament House, led by the horse-mounted bodyguards.
They were received at the gate by Rajya Sabha Deputy Chairman K Rahman Khan, Lok Sabha Speaker Somnath Chatterjee and Chief Justice K G Balakrishnan.
Reportage: Onkar Singh & Agency Inputs
Photograph courtesy: Rashtrapati Bhavan