By the end of Tuesday's voting, Najib Mikati had 68 votes. Caretaker Prime Minister Saad Hariri had 60.
The Shiite militant group is now in position to control Lebanon's next government. The move has set off angry protests and drew warnings from the U.S. that its support could be in jeopardy.
Thousands of Sunnis waved flags, burned tires and torched a van belonging to Al-Jazeera on Tuesday during a "day of rage" to protest the gains by Hezbollah.