The election signals a new era for politics in Kosovo, previously dominated by figureheads from the country's late-1990s war.
The opposition leftist Vetevendosje (Self- determination) party looked set to come first in Kosovo's parliamentary poll, but it will have to negotiate a coalition to form a government.
Preliminary results showed it had won 26% of votes with 82% of ballots counted, while another opposition party — the centre-right Democratic League of Kosovo (LDK) — won 25% of votes.
Supporters celebrated in Pristina on Sunday evening.
The early election happened after Prime Minister Ramush Harra-din-aj resigned ahead of questioning in the Hague by an investigation into war crimes in Serbia two decades ago.
The Democratic Party of Kosovo (PDK) was third with 21% while a list headed by the outgoing prime minister, Ramush Haradinaj, got 11.5% of votes.
It signals a new era for politics in the Balkan nation, whose leadership was previously dominated by figureheads from the country's late-1990s ethnic conflict and war of independence.
Kosovo became independent from Serbia in 2008.
Key issues for voters were the country's deep-rooted corruption and a peace deal with Serbia that would pave the way for membership of the United Nations.
The election was called after Haradinaj resigned in July when he was summoned to appear before a war crimes court.
There have been questions around Haradinaj's role in the 1998-99 war as one of the commanders of the former Kosovo Liberation Army who fought for independence from Serbia.
According to opinion polls, public dissatisfaction with Haradinaj's record at the head of a three-party governing coalition has boosted support for opposition parties.
Kosovo's election is overseen by more than 34,000 monitors, including 100 from the European Union.
The peace deal with Serbia is central in the electoral debate.
Twenty years after Serbian forces were expelled from Kosovo by NATO bombing, Belgrade refuses to recognise Kosovo as independent. Serbia, and its ally Russia have blocked Pristina's membership of international organisations including the United Nations.
In 2013, Pristina and Belgrade agreed to an EU-mediated dialogue to normalise ties but little progress has been made.
Talks with Serbia
Last year, Kosovan President Hashim Thaci and Serbian President Aleksandar Vucic signalled that they might agree to a land swap but they faced strong opposition to the idea domestically and abroad.
In Kosovo, all three parties LDK, Vetevendosje and PDK said the land swap was not acceptable.
The United States and the European Union see lingering, unresolved tensions between Belgrade and Pristina as a major threat to regional stability and are pushing for a normalisation of ties.
On Thursday, U.S. President Donald Trump appointed Richard Grenell, the straight-talking U.S. ambassador to Germany, as special envoy to try to inject new energy into the talks between Belgrade and Pristina.
Kosovo has Europe's youngest population, with an average age of 29, and has seen annual economic growth averaging 4% over the past decade, but it remains poor. Since Pristina won independence from Belgrade in 2008, more than 200,000 Kosovars have emigrated and applied for asylum in the European Union.
"It hurts me when I see young, educated people from Kosovo coming to Germany because they don't see a better future here," Skender Nekaj, 44, who came from Germany to Kosovo to vote together with seven other family members, told Reuters.
The public sector is the biggest employer in the country but an applicant typically needs political connections or to pay a bribe to find a job.
The European Union says corruption is "widespread" and Transparency International ranks Kosovo as a very corrupt country.
"If you have money you can buy justice here, if you have money you can buy health because you go to a private clinic. I don't have money. My vote is the only thing I have," Qendrim Agushi, 32, a construction worker who earns 13 euros a day, told Reuters.