The son of Togo's long-serving leader, Gnassingbe Eyadema, has been inaugurated as president following last month's disputed elections.
Mr Faure has already taken the oath of office once this year
Faure Gnassingbe, 39, was confirmed winner of the polls on Tuesday, when the Constitutional Court rejected an opposition claim the poll was rigged.
Security is tight in the capital after violent opposition protests last week.
Mr Faure was initially sworn in after his father's death but international pressure led him to step down.
On Wednesday, in front of members of the Constitutional Court and officials, he said he would concentrate on "the promotion of development, the common good, peace and national unity".
"I vow to loyally fulfil the highest functions that the nation has conferred upon me and to be guided by the general interest and the respect for rights and human beings," he said.
The BBC's Ebow Godwin in the capital, Lome, says the city is calm and schools have reopened for the first time since last month's elections.
The Constitutional Court had said the opposition appeal that the election had been rigged, "lacks substance, evidence and merit".
Opposition leader Gilchrist Olympio told the BBC that he rejected the court's ruling and said his party would not join a transitional government, as urged by West African regional grouping Ecowas.
Thousands have fled Togo since the election
An Ecowas observer told the BBC on Wednesday that he saw "irregularities" during the polling.
Martin Assogba said that in one polling station in Mr Faure's northern stronghold, more ballots were cast than there were registered voters.
However, the official Ecowas delegation says the elections were broadly free and fair, despite a few isolated problems.
Thousands of people have fled Togo for neighbouring Benin and Ghana as a result of the political violence since the election.
At least 22 people died in unrest, mostly in areas of Lome where opposition support is strongest.
The BBC's Elizabeth Blunt, who covered the elections, says Mr Faure is going to need all his charm if he is going to knit Togo back together after an acrimonious campaign and what the opposition believe was a stolen election.
And he also has to woo international donors, especially the European Union which cut off all development aid 12 years ago because of his father's excesses.