European hornets are social wasps that form colonies lasting for one year. They prefer to build their paper nests in hollow trees, barns, and outbuildings, but they will also nest inside the walls, attics, or chimneys of buildings. Nests may even be constructed on the sides of buildings. Like yellowjackets and bald-faced hornets, European hornets aggressively defend their colony if it is disturbed. Loud vibrating noises from lawn mowers and leaf blowers can provoke hornet workers to sting people and pets. Colonies of European hornets may contain several hundred workers.

Removing their nest is the only effective way to eliminate a hornet colony, and this should only be done by an experienced professional. The danger of stings is significant, so proper protective clothing and equipment are required.