The final results of Poland's election show the liberal Civic Platform party with 41.51% of the vote.
Donald Tusk's party will get 209 seats in the 460-seat lower house of parliament, the Sejm, the national electoral commission has announced.
The ruling conservative Law and Justice party of Prime Minister Jaroslaw Kaczynski and his identical twin, President Lech Kaczynski, won 32.11% of Sunday's vote and 166 seats.
Only two other parties surpassed a 5% limit required for representation in the parliament.
The Left and Democrats, an alliance steered by the ex-communist Social Democrats, got 13.15% of the vote, won 54 seats.
While the moderate Polish Peasants' Party won 8.91% of the vote and 30 seats.
Civic Platform is expected to form a ruling coalition with Polish Peasants' Party because they already run several local governments together.
The Civic Platform leadership has announced that no final decisions on a coalition will be made until 10 November.
Under the Polish constitution, a new parliament must hold its first sitting within 15 days of an election.
The Polish president then has 14 days to formally appoint a prime minister and the other members of the new government, who must then win the approval of parliament.
The remaining seat in the Sejm went to a representative of Poland's German minority, whose parties only put up candidates in a handful of constituencies and are not required to clear the 5% national hurdle.
The populist Self-Defence party and far-right League of Polish Families were swept from parliament in Sunday's vote, receiving just 1.53% and 1.3% of the vote respectively.
Poles also elected members of the 100-seat Senate in Sunday's contest.
Civic Platform won 60 seats and Law and Justice won 39.
One independent, the former Social Democrat prime minister Wlodzimierz Cimoszewicz, was also elected.
Turnout was 53.8%, the highest rate for parliamentary elections since the end of communism in 1989.
