Yanmega is a large, dark green dragonfly Pokémon. Its large eyes are red with black lines that make a sideways "T" shape in each one. It has two large, white fangs or mandibles next to its small mouth. Its immense jaw power allows it to bite apart foes while flying by at high speed. Each of Yanmega's segments has a red spot on them, while the last tail segment has a black triangular plate. It has two similar plates on the back of its thorax and a third on its head. Yanmega has six black thin legs. It has four white, oval wings with red tips, and there are two smaller white wings on the end of its tail.

Yanmega can create shock waves by beating its wings. These shock waves are so powerful, they may inflict critical injuries on any foes or even knock down huge trees. Yanmega's wings are powerful enough to carry an adult human. Yanmega is very rare in the wild, though it can be found in wooded and swampy areas. It has very strong jaw power and bites apart its prey's heads while flying at high speed. Yanmega usually aim for the prey's most vulnerable spot, wasting no energy in the process. Yanmega is said to be an extremely violent Pokémon, usually requiring someone of incredible bravery to tame this aggressive bug. When Yanmega needs to rest, it flips its body over and finds a branch to rest on.