Eighty four out of 173 doctors resigned after failing to reach a pay deal with management at the hospital in Czestochowa. They were due to stop working on Monday.
Ambulances transported some 40 patients, including new-born babies, to hospitals in neighbouring towns.
The Polish doctors' union OZZL said several other hospitals were in the same situation, and that some 5,000 Polish doctors had resigned in pay disputes.
Doctors in some 200 Polish hospitals went on strike in May to seek rises in salaries that remain very low compared with other professions.
A Polish doctor's basic net salary is not more than 1,500 zlotys (416 euros, 568 dollars) per month, or 9.9 zlotys (2.6 euros, 3.7 dollars) per hour, while a cleaning lady can earn up to 12 zlotys per hour.