The Cambodian People's Party (CPP) of the strongman leader won 68 seats to 55 for the opposition Cambodia National Rescue Party, according to a notice on the website of the country's National Election Committee.
The results end the legal avenues open to the opposition to contest the poll, despite its allegations that major voter fraud distorted the result and a mass rally of some 20,000 supporters on Saturday calling for an independent probe into the election.
Cambodia has been in a political deadlock since the July poll, with a defiant Hun Sen vowing to continue in power despite vociferous calls from opposition leader Sam Rainsy for a probe into voter fraud.
Experts say the result is a blow to the CNRP which was adamant it had won the election, however it also represents a significant parliamentary gain on the last election.
Hun Sen, 61, a former Khmer Rouge cadre who defected and oversaw Cambodia's rise from the ashes of war, has vowed to rule until he is 74.