The chief justice of Botswana says the governing Botswana Democratic Party has won the parliamentary election, BBC reported.
The victory gives President Ian Khama another five years in power in the world's largest diamond producer.
So far, the BDP has won 36 of the 57 seats contested, with the count complete in 45 constituencies.
The main opposition party, the Botswana National Front, and the Botswana Congress Party have won four seats each with one going to an independent.
The BDP has been in power since independence in 1966.
The turnout in Friday's election was reported to be high, and election observers said voting went smoothly.
Final results were expected to be announced at lunchtime on Sunday, said a spokesman for the country's Independent Electoral Commission.
Although the global slowdown has caused gem sales to decline and some Botswana diamond mines closed earlier this year, the country remains one of Africa's most stable democracies.
The election was Mr Khama's first democratic test since becoming Botswana Democratic Party (BDP) leader some 18 months ago.
The son of Botswana's first president, he is credited with being decisive, but also criticised for being dogmatic.
Friday's turnout was high, said the BBC's Letlohile Lucas in the capital, Gaborone, and voting hours were reportedly extended to cater for queues outside many polling stations.
One Gaborone voter said the election campaign had been more exciting than in previous years.
"We saw a lot more debates and people have been a lot more vocal," Malebogo Morakaladi told AFP news agency.
Botswana's over-dependence on diamonds for its export earnings and tax revenues, as well as jobs and human rights, were expected to be issues influencing voters, analysts suggested.
"I would like them [the new government] to improve the employment rates in Botswana, especially for the young people, and I'd like development in the rural areas and water in the rural areas," a Gaborone voter told the BBC's Network Africa programme.
The election saw a few instances where people had been unable to vote, although overall the voting seemed "smooth", Dumelang Saleshando from the opposition Botswana Congress Party told the BBC.
Recent moves to slap a 30% levy on alcohol, clamp down on the media and impose strict discipline on party dissidents have led to criticism that Mr Khama is too authoritarian.
The 56-year-old president has dismissed the charges, and says he is a man motivated by delivery who is simply media-shy.
The BDP won 44 seats at the last election in 2004, with the other seats going to the Botswana National Front and the Botswana Congress Party.