Adam Niedzielski said the “Good Samaritan” rule would “allow doctors to feel safe”.
He added that medical staff who are not infectious-disease specialists would be brought in to help fight the epidemic.
Some Polish doctors have voiced concern, pointing out that they have not been trained to treat coronavirus patients.
Poland reported a record daily rise in COVID-19 infections for the second consecutive day on Thursday, confirming 8,099 new cases, the most since the pandemic hit the country in early March.
Niedzielski said that medical staff deployed to help fight the coronavirus would receive extra pay.
Prime Minister Mateusz Morawiecki on Thursday announced tougher rules aiming to limit infections, with the number of “red” zones - those with the most severe restrictions - to be upped so they cover almost half the country.
Niedzielski told reporters: "We must be aware that we are testing the limits of the capabilities of the health service".