Yameen, the half-brother of former autocratic ruler Maumoon Abdul Gayoom, was administered the oath of office by Chief Justice Ahmad Faiz at a special session of the Parliament. He was given a 21-gun salute.
Mohammad Jameel was sworn in as vice-President.
Yameen, 54, an economist and a candidate of Progressive Party of Maldives, clinched an unexpected victory in the presidential run-off yesterday by receiving 51.39 per cent of the votes over opposition leader and former president Mohammed Nasheed who garnered 48.61 per cent of the votes.
In his inaugural speech, Yameen said he will protect the gateway to Maldives, a popular tourist destination.
"I shall strive to make the Maldives the safest and most developed nation in the region. We will maintain good neighbourly relations with countries in the region," he said.
Two former presidents -- Nasheed and Maumoon -- also attended the swearing in ceremony.
Presidential spokesperson Imad Masood said over 50-members attended the special session of the Parliament.
Earlier, Elections Commission announced the official results of the presidential runoff, confirming Yameen, the half-brother of former autocratic ruler Maumoon Abdul Gayoom, as the president elect.
Elections Commissioner Fuad Thowfeek announced that Yameen garnered 111,203 votes and Nasheed received 105,181 votes.
According to Fuad, the voter turnout for the run-off was 91.41 per cent with 218,621 people voting in Saturday’s polls.
After the results were declared, Yameen said the country desperately needed stability and hoped his opponents would cooperate.
"The country needs stability," Yameen told reporters. "I hope we will receive the necessary cooperation from Nasheed through parliament."
"Instead of confronting political leaders, we will confront the big challenges facing our country," he said.
Maldives has witnessed political turmoil since 46-year-old Nasheed resigned under duress in February 2012 in a controversial transfer of power.
Nasheed conceded defeat in yesterday's run-off after a bitterly fought battle and said he was pleased that the country finally had a democratically elected leader.
"The MDP has always asked for a government elected by the people," Nasheed told reporters.
"Today is a happy day for the Maldives -- we now have an elected government."
The Maldives had failed to elect a president in three attempts since September, raising concerns in the international community that the fledgling democracy may slip back to authoritarian rule.
The international community led by the US and India had called for the democratic process to be resumed. The Commonwealth, European Union and the US had called for democratic process to be observed.
In the first round of elections held in September, Nasheed led over Yameen and Jumhooree Party candidate Gasim Ibrahim but failed to secure a more than 50 per cent of the votes.
But before a run-off could be held, the results were annulled by the Supreme Court which cited irregularities in the voters' list.
A second attempt to hold the polls on October 19 was thwarted by police after a Supreme Court ruling.
The re-vote finally took place on November 9 and Nasheed again comfortably led in the first round but could not cross the half-way mark, resulting in yesterday's run-off with Yameen.
The Commonwealth on Thursday suspended the Maldives from its disciplinary panel, a first step towards expulsion from the 53-member organisation for failing to uphold its shared democratic values.
Yameen will be the second democratically-elected President on the Maldives.
Photograph: Haveeru/Reuters
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