Yamper is a quadrupedal, canine Pokémon. It has a brown body with yellow fluff around its neck, resembling a collar, and yellow highlights around its eyes. It has a yellow bolt-shaped tail and a heart-shaped pattern on its rear. Its four feet, underside, and parts of its face are white. Yamper's ears have a light green and yellow color on the inside. It also has a small yellow nose.
Yamper tends to be drawn to fast-moving things and will chase after people, other Pokémon, or even vehicles. Yamper has an organ that generates electricity from the base of its tail when it runs. It cannot store the electricity it generates, so sparks of electricity can often be seen when it is running. In the Galarregion, it is a popular choice for herding Pokémon such as Wooloo. Due to its gluttonous nature, it will only assist people in exchange for treats.Joltik are often seen on its hindquarters, feeding on its static electricity.