Former human rights lawyer vowed to put Ghana "back on path of prosperity" after economic slump under President Mahama.
Nana Akufo-Addo has been sworn in as Ghana’s new president after beating incumbent leader John Mahama in last month’s election.
Heads of state from across Africa and thousands of guests and dignitaries watched him take the oath of office at a ceremony in the capital, Accra.
Mr Akufo-Addo, a 72-year-old former human rights lawyer, promised free high school education and more factories.
But critics have questioned the viability of his ambitions.
Mr Akufo-Addo repeated the presidential oath after it was read out to him at a ceremony in the capital’s Independence Square on Saturday.
Taking the oath of office, which represents the latest peaceful handover of power in the country, Mr Akufo-Addo promised to "protect and defend" Ghana’s constitution.
He later posted the full text of the presidential oath on the social media site Twitter, using the hashtag #Inauguration2017.
Mr Akufo-Addo, from the New Patriotic Party, was elected on his third attempt to reach the post, after a campaign dominated by the country’s faltering economy.
Major roads in and around the capital were cordoned off for Saturday’s event.
72 years old
Human rights lawyer
Campaigned for a return to multi-party democracy under military rule
A former justice and foreign minister in the NPP government from 2001 to 2007, he is running for president for a third time
His main promise was to build a factory in each of Ghana’s more than 200 districts
Mr Akufo-Addo has vowed to revive the country’s economy, saying that "there are brighter days ahead".
An economic slump under Mr Mahama led to an International Monetary Fund bail-out.
The former president has defended his record, saying his government had been up against "strong headwinds" that caused growth to slow, public sector debt to rise and the country’s currency, the cedi, to fall.
Ghana has been a multi-party democracy since the end of military rule in 1992 and the transition is seen as reinforcing its reputation for the peaceful transfer of power between administrations.
- Nana Akufo-Addo takes the oath of office during a ceremony at Independence Square in Accra