The ovipositor or the stinger is around 6 millimetres long and produces a very strong venom that can damage tissue by stimulating phospholipase. A sting from the Japanese hornet for a person with allergies is almost definitely fatal with many people without allergies with a strong enough sting are likely to die.

The venom from a Japanese hornet contains at least 8 distinct chemicals. Some of the chemicals in the venom damage tissue, cause pain and one that is a pheromone that attracts other hornets to attack. The Japanese hornet is a hunter who preys on many insects including bees, other hornets and mantises. They also feed on honey bee larvae, killing all honey bees that get in their way with ease. A single Japanese hornet can kill 40 honey bees in a single minute, with many Japanese hornets destroying a hive of 30,000 honey bees in a matter of hours.