The main opposition Democrats won 28 seats while the Republican Bloc (BR) and Progressive Union for Renewal (UP-R) parties allied with President Patrice Talon together won 81 seats in Sunday's ballot, the CENA electoral authority said.
Final results are expected on Friday after a vote that went ahead peacefully and in line with the regulations, according to election observers.
Four years ago opposition parties were effectively barred from participating in a legislative ballot due to a tightening of election rules, resulting in a parliament dominated by Talon supporters.
Most of Talon's key opponents have also been jailed or forced into exile.
The 2019 vote was marred by deadly clashes in an opposition stronghold, historic low turnout and an internet blackout.
Talon, a cotton magnate first elected in 2016 and re-elected in 2021, has promoted political and economic development but critics say that has come at the cost of stifling Benin's once-vibrant multi-party democracy.