Poland first shut its borders on March 15 for 10 days.
Interior Minister Mariusz Kamiński told a news conference on Wednesday that goods would continue to be allowed into the country.
He added that new restrictions would be introduced on Poles who cross the border because they work abroad.
"From Friday, these people who cross Polish borders will be subject to a two-week quarantine,” he said.
Kamiński added that during the epidemic the free flow of workers into Poland could not be allowed, especially from countries where the number of coronavirus infections is higher.
Polish authorities said on Wednesday that three more coronavirus patients had died in this country, bringing its total death toll from the COVID-19 disease to 13.
The number of confirmed coronavirus cases in Poland rose by 57 on Wednesday, bringing the total to 957.
The Polish government has declared a "state of epidemic" as it battles the outbreak.
International scheduled flights and passenger rail connections were suspended on March 15. The government is chartering special flights to help citizens abroad return home.
Poles have been told they cannot gather in groups of more than two, though families are exempt from the restriction.