A herd of bison, Europe's largest land mammal, crossed the tracks as a train carrying about 50 passengers passed at full speed on Sunday morning near the village of Witowo.
No passengers were injured, but three animals died in the accident, police spokesman Konrad Karwacki told AFP.
The “Zubr” train, which takes its name from the Polish word for bison, did not derail and was able to resume its journey about an hour and a half after the collision.
There are around 1,200 bison in the Polish part of Bialowieza, the last large primeval forest in Europe, which is divided by the border with Belarus.
