Pohiva Tu'i'onetoa, the current Minister of Finance, has won convincingly with 15 votes, to acting Prime Minister Semisi Sika, who got 8 votes.
Mr Tu'i'onetoa, who was a minister in good standing in the Pohiva government, earlier this week crossed the floor to form the new People's Party and gain the support from a united group of nobles and independent MPs.
Three other MPs who were part of Mr Pohiva's party, also crossed the floor.
The defection of the four members of Pohiva's party meant the party was unable to have a majority in electing the prime minister.