But the victors face tough coalition talks on splits over how far to go in embracing the free market.
Exit polls indicate the biggest triumph for the heirs of the Solidarity movement which helped trigger the fall of communism in 1989.
With 60% of the votes counted, the victory for the centre-right was slightly less impressive than suggested by exit
polls on Sunday.
The vote count gave the Catholic Law and Justice party (PiS) 26.56% of the vote, and a likely 151 seats in the 460-seat parliament.
The free-market Civic Platform was second with 24.08% of the vote, and a likely 123 seats.
The two parties have confirmed their intention to form a coalition, which the vote assures a comfortable majority.
"We have long said we want this coalition and there are no reasons why it shouldn't happen," said Law and Justice leader Jaroslaw Kaczynski, likely the next prime minister.
Both parties promise to create more jobs, lower taxes and weed out corruption that tainted the four-year rule of the Democratic Left Alliance, reformed former communists.
But financial markets believe a coalition led by the Civic Platform would more aggressively tackle Poland's pressing economic problems of unemployment (at 18%, the highest in the EU), bloated budgets and costly social security.
Reflecting a wider European debate, the two parties also differ on how much welfare Poland, whose wealth levels are half the EU average, can afford.
Jaroslaw Kaczynski, PIS leader,
is likely to be the next premier
The Civic Platform, which has pledged to move fast with tax cuts, deregulation, privatisation and euro adoption, barely hid its disappointment that the conservatives' tough talk on crime and vows to uphold the welfare state secured them victory.
"The Law and Justice programme at its core is socialist and Poland is fed up with socialism."
"I think that voters with socialist views were orphaned by the collapse of the left and shifted to Law and Justice," Bronislaw Komorowski, a Civic Platform leader, said.
The conservatives' lead over Civic Platform disappointed investors, who piled into the Polish zloty, bonds and stocks when opinion polls suggested earlier this month that free-market champions would lead the next cabinet.
Economists said the zloty was set to weaken when markets opened on Monday, also reflecting concern that the campaign for presidential polls on 9 October may disrupt coalition talks.
"The presidential campaign is still going on, so the battle between the Platform and Law and Justice will continue," said Ryszard Petru, chief economist at Bank BPH in Warsaw.
"The presidential campaign is still going on, so the battle between the Platform and Law and Justice will continue"
Chief economist, Bank BPH
The 9 October vote, which could go into a run-off two weeks later, pits Civic Platform leader and front-runner Donald Tusk against conservative Warsaw mayor Lech Kaczynski, twin brother of fellow Law and Justice leader.
The parliamentary campaign exposed the rift between the growing middle class, which wants more free-market openness, and those who feel left behind after 16 years of painful reforms.
Political analysts say the Kaczynskis cleverly tapped that anger, painting the Civic Platform proposal of a 15% flat tax as a gift for the rich at the expense of the poor.