Unlike his predecessor Alexis Tspiras back in 2015, Mitsotakis took a religious oath of office with his hand on the Bible in the presence of the Archbishop of Athens, Ieronymous II, and several other Orthodox representatives in a traditional ceremony at the presidential palace, reported Efe news.
"I swear in the name of the Holy, Consubstantial and Indivisible Trinity to safeguard the Constitution and the laws and to serve the general interest of the Greek People," he said, joined by President Prokopis Pavlopoulos, his wife and three children.
In a brief statement before heading off to the government headquarters to exchange functions with Tsipras, Mitsotakis reiterated the message he gave on election night: "The people have given us a strong mandate to change the country. From today we will begin to work very hard," he said.
Tsipras welcomed him with a handshake, something that the outgoing PM's predecessor, the conservative Andonis Samaras, did not do in 2015.
New Democracy took 39.8 per cent of the national vote in Sunday's elections, meaning it landed 158 of the 300 parliamentary seats, while Syriza dropped to 31.5 per cent, or 86 lawmakers.
Under Greek norms, the winning party is awarded 50 bonus seats.
The results make way for bipartisanship in Parliament once again, as Syriza comprises a strong opposition force, with a 20-point advantage over its nearest challenger, the centrist Kinal party.
New Democracy obtained its best showing in more than a decade, as voters fled not only Syriza but several other major parties towards the centre-right.
The outgoing governing party secured just four points less than what it achieved in 2015.
Kinal scraped 8 per cent, two percentage points more than its previous showing.
The communist KKE held onto its 5 per cent share, largely thanks to the collapse of the neo-Nazi Golden Dawn, which took just 2.9 percent, less than half of what it achieved last time around and not enough to make the cut for parliamentary seats.
This does not indicate that the hunger for the far-right was ebbing in Greece, as Greek Solution took 10 seats, or 3.7 per cent of the vote.
( With inputs from IANS )