The election was expected to return President Emomali Rakhmon to office
The opposition in Tajikistan has said it will mount a legal challenge to the results of parliamentary elections.
The election commission said President Imomali Rakhmon's party won almost all the seats in the lower house of parliament in the election.
It said the opposition Islamic Revival Party won two seats, and five went to minority parties including the communists.
Voting was marred by widespread fraud, international monitors have said.
The Organisation for Security and Co-operation in Europe (OSCE) said the polls had "failed on many basic democratic standards".
"The election results, though preliminary, are unfair. There was massive falsification. We find it hard to explain this to our constituents," opposition party chief Muhiddin Kabiri told reporters.
"We will take action within the laws of Tajikistan. The Islamic Revival Party is the party of the people. We will express our protest following the legal path in court."
Mr Kabiri said that his party won around 30% of the vote, and not 7.7% as claimed by the Central Elections Commission.
"We will decide whether to take part in the incoming parliament, or whether to declare a hunger strike or organise a rally," he said.
President Rakhmon's People's Democratic Party was said by the election commission to have won 45 of the parliament's 63 seats. An additional nine nominally independent seats went to local leaders seen as loyal to the president.
Election officials claimed a 87.1% turnout, a massive amount in a country where at least one million men are estimated to have fled the country in search of work.
The ruling party earlier said there had been minor violations to the poll which would not affect the will of the Tajik people.
The observers from OSCE and the European Parliament said there had been "serious irregularities" on polling day, including a high prevalence of family and proxy voting and cases of ballot box stuffing.