He's to form a coalition government to drive through the unpopular austerity measures demanded by Greece's creditors.
Eight months after his first swearing in, Alexis Tsipras took the oath of office again.
After his left-wing Syriza party won 145 seats in the country's 300-seat parliament in the country's snap election, the Prime Minister has a fresh mandate to apply the tough economic reforms he signed on to in July, in return for Greece's third international rescue in five years.
He's promised to revive the nation's crippled economy.
"We are committed and dedicated to do anything in our power in order for the country and the people to exit this tremendous hardship, for our country to become once again powerful, an equal partner within the European Union and our people proud and dignified."
Mr Tsipras will once again form a coalition government with the small nationalist Independent Greeks (ANEL) party.
Its leader, Panos Kammenos, has promised to build on the previous coalition's work.
"We will proceed with the reforms but at the same time we have to prepare policies to protect the people, to protect the four million in unemployment."
Mr Tsipras called the election after his party split a month ago, with rebels denouncing him for agreeing to implement tax increases, spending cuts and market reforms demanded by creditors in return for another bailout.
A member of the defeated New Democracy party, Niki Kerameus, says the election been a further blow to the economy.
"What today's result proves is that this election was completely unneeded because we're back to exactly more or less the same forces of the two main parties of Syriza and New Democracy, same MPs so nothing has changed but what has changed is that this election had a tremendous hit yet again on Greece's economy."
One of Mr Tsipras' first duties will be representing Greece at an emergency summit on Wednesday of European leaders to discuss the worsening refugee crisis.
He's calling for the European Union to better assist reception countries including Greece.
