Loop PNG reports O’Neill was sworn in by Governor General Sir Bob Dadae in Parliament yesterday afternoon.
After his People's National Congress emerged as the party with the most MPs from PNG's lengthy national election, Mr O'Neill has gained enough support in the parliament to begin a second five year term in the position.
The Ialibu-Pangia MP-elect was nominated by Abau MP Puka Temu, before Mt Hagen MP William Duma seconded the motion and Tari MP James Marape closed the nomination.
He won the vote 60 to 46, a significant decrease in the majority that Mr O'Neill commanded in the past term.
The opposing group known as the Alliance, based around the next two biggest parties - the National Alliance and the Pangu Pati - stayed intact from its pre-parliament camp.
The straightforward vote took place in near solitude, a far cry from the chaos in which the tenth parliament began this morning with results still not finalised in several of the 111 seats.
MPs-elect convened at the national legislature in Waigani this morning amidst heavy security for the respective votes for speaker of parliament and then prime minister.
However, the sitting had barely begun when it came to an impasse after another election controversy emerged.
Two men in the chamber were claiming to be the MP-elect for the Gumine seat: Nick Kuman from the People's National Congress party, and Lucas Dekena of the PNG Party.
Mr Kuman was earlier confirmed by the Electoral Commission as Gumine's MP-elect, but due to challenges to the legality of the person who purported to be the Gumine returning officer when declaring him, the election result remains questionable.
The hold-up came when both Mr Kuman and Mr Dekena refused to vacate the chamber, prompting scenes of anger and confusion as dozens of MPs called for parliament to be adjourned.
Due to the fracas, the Chief Justice Sir Salamo Injia was initially prevented from swearing in the newly elected MPs.
The MP-elect for Sinasina-Yonggamugl Open, Kerenga Kua, was the most vocal, urging the Chief Justice to not allow parliament to proceed with lingering uncertainty over results in at least several seats.
Shouting across the chamber, Mr Kua said the chaos was a reflection of the inadequate performance of the Electoral Commissioner Patilias Gamato who presided over what has been described by many as PNG's most chaotic election yet.
Photo by Loop PNG