"The security of the external borders of the European Union" will be one of "several issues" discussed by the two leaders at their meeting amid a "serious crisis" on Poland's eastern border with Belarus, the government spokesman, Piotr Müller, said.
He added that Poland enjoyed the support of "both the European Commission and NATO" amid a migrant surge.
He also said that Morawiecki would brief Merkel on the situation on the Belarus border.
During the meeting, the Polish prime minister "expects to hear a direct confirmation of support" from Merkel's Germany amid the border crisis, Müller told an online broadcaster.
Polish President Andrzej Duda said on Thursday that his country was making every effort to safeguard the eastern frontier of the European Union from an influx of illegal migrants crossing from Belarus.
Morawiecki last week said the authorities in Minsk were responsible for the migrant surge.
"Not an hour passes without the Belarus authorities transferring migrants to the Polish border, from Iraq, Syria, Afghanistan, Lebanon, Egypt, Somalia--anywhere they can attract them," Morawiecki told a news conference at the time.
Fellow EU members Lithuania, Latvia and Estonia have also accused Belarus' strongman leader Alexander Lukashenko of organising a wave of illegal migrants seeking to enter the bloc, as part of what officials have called a "hybrid war," Poland's PAP news agency reported.
Last week, Poland declared a state of emergency in parts of two regions bordering Belarus.
Morawiecki, Merkel to discuss 'desired shape of EU' amid tensions
Morawiecki and Merkel are also expected to discuss "the desired shape of the EU" when they meet in the Polish capital on Saturday, amid "tensions inside the bloc," Müller said in a media interview.
"Germany's voice on the European project and its workings is significant for the future of the EU," Müller also said on Thursday.
Merkel is relinquishing the reins of government after 16 years in power and Saturday's trip will be her last to Warsaw as chancellor, the PAP news agency reported.