Ulisses Correia e Silva's centre-right MpD, which held 40 seats in the outgoing parliament, is expected to win the 37 deputies needed for an absolute majority.
Cape Verde's prime minister has declared victory after results showed his party on course to win legislative elections dominated by the Covid pandemic and its impact on a tourism-dependent economy.
"It's a great victory, the victory of Cape Verde," Ulisses Correia e Silva said as jubilant supporters gathered in front of his party's headquarters in the capital of Praia.
"We succeeded in convincing Cape Verdeans of the correctness of the government's conduct in a very difficult time and the correctness of our proposals for the future," he added.
The 58-year-old leader's Movement for Democracy (MpD), in power since 2016, had won 36 of the 72 seats in the country's National Assembly by the end of the evening, according to results from 95 percent of polling stations tallied by the electoral commission.
The results for four seats devolved to overseas Cape Verdeans in the Americas, Europe, and Africa have not yet been counted.
The MpD is nevertheless well ahead of the opposition African Party for the Independence of Cape Verde (PAICV), which ruled the former Portuguese colony when it was a one-party state, led by Janira Hopffer Almada.
Results suggested the party would win 26 seats, dashing the 42-year-old lawyer's hopes of becoming the country's first female leader.
After voting, Almada complained the ruling party continued campaigning after the official end of electioneering on Friday, calling it a "grave violation".
Cape Verde has a semi-parliamentary system in which the prime minister wields executive power while the president plays the part of the arbitrator in the event of intractable disputes.
Elections for the presidency take place on October 17.
'Fight Covid and develop the economy'
With foreign tourism accounting for roughly a quarter of the economy and visitors unable to come because of global pandemic restrictions, Cape Verde, with a population of 550,000, was plunged into a historic recession in 2020, when output shrank by 14.8 percent.
Both major parties have pledged measures to provide wide access to Covid-19 vaccinations and to diversify the economy.
"The priority for me is to re-elect the government, fight Covid and develop the economy and tourism," said Luis Leit, 44, after voting in the capital Praia.
Although it lies around 600 kilometres (375 miles) off the coast of Senegal, Cape Verde has witnessed a surge in coronavirus infections.
With 189 cases per 100,000 inhabitants, the country had the highest rate in Africa, according to the Africa Centres for Disease Control and Prevention for the period from April 5 to 11.
Polling stations closed after 11 hours of voting, with just over 392,000 people registered to cast their ballots.
In a continent marked by political unrest, coups, or monolithic rulers who have been in power for decades, the tiny Atlantic archipelago stands out as a model democracy.
It ranks just behind Mauritius as the most democratic country in sub-Saharan Africa in the Economist Intelligence Unit's 2020 Democracy Index.
One-party rule in Cape Verde was swept away in 1990, and the first multi-party elections were held the following year.
In 2016, the MpD ended the PAICV's 15-year run with a historic victory, gaining 40 of 72 seats in the National Assembly.