Election officials in Chad say the president's party and its allies have won an absolute majority in parliament.
The electoral commission on Monday announced provisional results of a February 13 poll.
Officials say President Idriss Deby's party, the Patriotic Salvation Movement (MPS), and aligned parties captured at least 130 out of 188 seats.
The election was Chad's first legislative poll in nearly nine years.
International observers said while some polling centers opened late, they did not see any irregularities aimed at fraud.
Opposition parties boycotted the last national election in 2006, a presidential poll won by Deby.
The opposition signed an accord in 2007 that eventually paved the way for Sunday's voting.
Tension flared ahead of the poll in December, when the head of the electoral commission was fired after the opposition accused him of irregularities.
President Deby has ruled Chad since seizing power in a 1990 coup. Under his rule, the nation has become an oil producer but remains locked in poverty.
He continues to be challenged by rebels in the east, who briefly invaded the capital in 2008.
President's Party Wins Chad Election
