Sara Duterte took the oath standing beside her parents, including her father President Rodrigo Duterte
Sara Duterte vowed to unite the Philippines at a ceremony in Davao.
It was there that the 44-year-old took over from her father as the city's mayor over a decade ago - before pursuing a career in national politics.
She took the oath beside her running mate, Ferdinand Marcos Junior, who will soon replace her father as president.
"The days ahead may be full of challenges that call for us to be more united as a nation," Ms Duterte said.
Her six-year term in office alongside Ferdinand Marcos Junior will formally begin on 30 June.
As candidates in May's elections the pair shored up historic landslide victories by forging a powerful alliance and running on a message of unity that helped many of their allies win power elsewhere in government too.
In the Philippines, the president and vice-president are elected separately.
Mr Duterte is a controversial "strongman" figure who came to power in 2016 promising to reduce crime and fix the country's drug crisis.
But critics say that during his five years in power, Mr Duterte has encouraged police to carry out thousands of extrajudicial killings of suspects in what he has called his "war on drugs".
The International Criminal Court has called for a formal probe into the thousands of killings that happened during the deadly crackdown.
Mr Duterte had initially said he would stand as vice-president, before changing his mind last month and announcing his retirement from politics.
On Sunday he stood beside his daughter as she was sworn in to the new role.
Ferdinand Marcos Junior - known by the nickname Bongbong - also attended the ceremony. Like his future vice-president, he too is the son of a former Philippines leader.
His disgraced father, with whom he shares a name, was driven from power as the country's dictator in a 1986 uprising.
Bongbong's election means that the Marcos family will now return after 36 years to power at the Malacañang - or presidential palace.
The Marcos family has never apologised for the abuses of the old dictatorship, nor given back much of the treasure they are accused of stealing from the national purse.
-- Courtesy of BBC News