Poland's ruling party Law and Justice (PiS) was backed by 42.4 percent of the voters. Its main opponent, the European Coalition received 39.1 percent of the votes.
According to the exit polls, the left-liberal party Spring received 6.6 percent of the votes. Fourth-placed far-right Confederation Korwin Braun Liroy Nationalists was backed by 6.1 percent of the voters.
The Kukiz'15 movement receiving a 5 percent backing and the Left Together with a 1.3 percent support found themselves below the electoral threshold and will not be represented at the EP.
If the result holds true, PiS would take 24 EP seats, European Coalition - 22 seats, Spring - 3 seats and the Confederation Korwin Braun Liroy Nationalists also 3 seats.
Among PiS politicians expected to sit in the EP are, among others, Beata Szydło, Joachim Brudziński, Anna Zalewska, Adam Bielan, Patryk Jaki, Jacek Saryusz-Wolski, Beata Kempa and Beata Mazurek. Meanwhile, Jerzy Buzek, Ewa Kopacz, Marek Belka, Leszek Miller, Włodzimierz Cimoszewicz, Radosław Sikorski and Danuta Huebner are among those to represent the European Coalition.
Ipsos estimated Sunday's turnout at a record level of 43 percent against 22.7 percent in 2014.
The official results are due to be released on Tuesday, according to the State Electoral Commission (PKW).
MEPs were chosen for a term of five years. Poles elected 51 European Parliament deputies, plus one more who will become active only when the United Kingdom leaves the European Union.
Voting to the European Parliament in Poland took place between 7 a.m. and 9 p.m. on Sunday. A total of 866 candidates (404 women and 462 men) are running in this year's European elections in Poland, according to the PKW. Over 27,286 polling stations were open to close to 30 million voters in Poland. Poles abroad voted at 203 polling stations.