Black and white footage from a surveillance camera in their pen shows the cubs playing with each other and cuddling with their mother Sizzel.
Germany's Spiegel magazine quoted the zoo director as saying the two cubs had their eyes open and that they were being looked after well by their mother.
According to the zoo director, the twins weighed around 1 pound at birth.
Now their weight is close to 13 pounds.
A polar bear's first few months of life are a critical phase and the Rostock twins will leave their cave in March at the earliest, according to the zoo.