The helicopter entered up to about 300 metres into Polish territory and remained there for 42 seconds, the Operational Command of Poland's Armed Forces said.
The helicopter breached Polish airspace at about 11:08 a.m. north of the northeastern town of Braniewo, the command said.
The machine was flying from Kaliningrad, the Russian exclave bordering Poland and Lithuania.
Polish radar systems tracked the helicopter, and fighter jets were scrambled while ground forces and equipment were placed on alert, the Operational Command said.
The incident indicated that Russia was "once again testing the readiness of our air defence," it added.
The incident came a day after Polish fighter jets intercepted a Russian Il-20 spy plane over the Baltic Sea about 40 kilometres off the Polish coast, according to Defence Minister Władysław Kosiniak-Kamysz.
"Russia regularly tests NATO's eastern flank--today again over the Baltic," Kosiniak-Kamysz said on Tuesday on X.
He described the incident as part of "constant pressure" rather than an isolated occurrence and said Polish airspace was under constant surveillance.
The Il-20 reconnaissance plane did not enter Polish airspace, according to Polish authorities.
Russian reconnaissance aircraft have been intercepted many times over the Baltic in recent months.
Polish authorities have said Russian military aircraft operating in the region sometimes fly with their transponders switched off and without filed flight plans, making remote identification more difficult and complicating the work of civilian air traffic controllers.
Intercepting unidentified aircraft near national borders is a standard procedure when there is no communication with the aircraft, Polish state news agency PAP reported.
Such Russian flights near NATO borders can also allow Moscow to observe the alliance’s responses and air-defence procedures, experts cited in Polish reports have said.
NATO’s Baltic Air Policing mission also monitors air activity in the region, with Polish and allied aircraft patrolling the airspace over the Baltic states and the Baltic Sea.
The latest incident was the first reported violation of Polish airspace by a Russian military aircraft in the area in recent weeks.
Russian aircraft intercepted over the Baltic had previously remained over international waters and did not cross into Polish airspace.
In August 2023, two Belarusian military helicopters briefly entered Polish airspace near the town of Białowieża in eastern Poland.
Warsaw responded by increasing the number of troops along the border and summoning Belarus’ chargé d’affaires to the foreign ministry to seek an explanation.