Sovaleni is the interim education minister, and is a former deputy prime minister.
He was the favourite to win the prime minister's seat, with a convincing lead emerging in recent days, and secured 16 out of 26 votes in the Legislative Assembly.
Sovaleni's election represents a change of government for the kingdom as his only rival candidate, 'Aisake Eke, had the backing of the former prime minister Pohiva Tu'i'onetoa.
RNZ Pacific correspondent in Tonga Kalafi Moala said the former prime minister made it clear that he was backing Eke in the hope the candidate would continue with the policies of the last government.
"If that group won it [meant] that we [were] going to continue in the same thing that has been done by the outgoing government. So Sovaleni winning means we have a whole new pathway into the future," Moala said.
Sovaleni's victory has been welcomed by many people in the kingdom who had gone into this year's election calling for change, he said.
Fresh faces, but no women
Tonga's general election was held on 18 November.
The country's 26-person legislature is made up of 17 People's Representative seats, and nine representatives elected by Tonga's nobles from among their 33 families.
Nine of the People's Representative MPs voted in are new faces, and there are three new faces in noble seats; Lord Vaea, Lord Fohe and Prince Fotofili.
Tonga has traditionally had few women in parliament, with only three holding seats since 2017. No women were elected this year.