Polish President Andrzej Duda has said he will give incumbent prime minister Mateusz Morawiecki the first opportunity to form a new government following elections three weeks ago.
His Law and Justice (PiS) party won 194 seats and faces a difficult search for allies to reach a majority of 231.
Three pro-opposition parties, led by former PM Donald Tusk, won 248 seats.
If Mr Morawiecki fails to secure enough allies, Mr Tusk could be given the chance to assemble a majority instead.
Mr Morawiecki is the leader of the ruling Law and Justice (PiS) party, which came first in elections to the Sejm, the lower house of parliament, last month but is far short of a majority.
All other parties in parliament have pledged not to support PiS.
After previous elections, the largest party was given the first opportunity to try to form a government. But given the difficulty Mr Morawiecki would face in securing a majority, the opposition had argued that Mr Tusk should be given the opportunity to agree a coalition.
Mr Duda, a PiS ally, took the decision after consultations with every party represented in parliament.
Mr Tusk's Civic Coalition (KO) and two allies, the Third Way and the Left, hold a comfortable majority of seats together.
PiS has been in power since 2015. In that time, Poland has frequently sparred with the EU over issues such as the rule of law and abortion rights.
A total of €36bn (£30bn) of EU funds earmarked for Poland have been blocked by Brussels because of concerns over the PiS government undermining the rule of law.
Earlier this month, Mr Morawiecki said he believed the decision by the Constitutional Tribunal to ban abortion in almost all cases - issued in response to a demand by PiS MPs - was "a mistake".
Parliament meets again on Monday and now has another 14 days to hold a confidence vote.
If Mr Morawiecki fails to win a vote of confidence for his new government, as seems likely at this stage, then parliament itself would designate a new prime minister.