Defensively, the Poison type is considered one of the best in the game. It is adept in both blocking and inflicting various status conditions, especially poison and bad poison. Its weakness to Ground can be mitigated by the variety of dual-type Grass and Bug/Poison Pokémon, as well as Poison/Flying types and Pokémon with Levitate. Additionally, the Poison type resists itself, Bug, Fighting, Grass, and Fairy (as of Generation VI), giving it resistances to a substantial number of common moves.
Similar to Ghost- and Bug-types, Poison-types tend to hold potent status and support moves, such as Toxic Spikes and Toxic. A grounded Poison-type Pokémon automatically removes Toxic Spikes on its side when it switches in. Although the majority of non-Poison types are able to learn Toxic, as of Generation VI, when a Poison-type uses the move, it gains perfect accuracy, bypassing accuracy checks and semi-invulnerable turns from moves such as Fly and Dig.
Poison-type moves are typically used to wear down foes by inflicting poison and bad poison to deal damage over time rather than to rely on basic damage. Prior to Generation VI, Poison only hit the Grass type super effectively, which was largely offset by the common Grass/Poison typing. Compared to Poison, Ice, Fire, Flying, and even Bug are much more useful in countering the Grass type. Aside from itself, Poison is resisted by Rock, Ghost, and Ground and is completely ineffective against Steel. (Steel is also immune to the Poison status condition.) Additionally, Poison types typically have average Attack and Special Attack, hampering the offensive usefulness of Poison-types.
However, as of Generation VI, Poison is one of only two types super-effective against Fairy, along with Steel, giving Poison a key offensive role. Because of the typically low Defense most Fairy types have, moves such as Poison Jab and Gunk Shot can often take them down in one hit.
Poison works well alongside Dark and Ghost offensively, since these cover Ghost-types as well as Psychic-types (which Poison-types are weak against), and Poison-types commonly learn Dark moves. It also pairs well with Ground, which covers Rock, Poison and Steel-types, and Water, which covers Rock and Ground-types.
In Contests, Poison-type moves typically become Clever moves. None of them are considered Cute.
As of Generation VII, there are 64 Poison-type Pokémon or 8.0% of all Pokémon, making it the 9th most common type.
Due to the decreased amount of types in the TCG, Poison-type Pokémon were generally listed as Grass Pokémon until the Diamond & Pearl set, but they have since been moved to being a part of the Psychic-type.
Poison-type Pokémon in the TCG are generally weak to Psychic Pokémon and they have no resistances. They were strong against Fighting and Water Pokémon prior to Diamond & Pearl, now however they are strong against the Grass, Fighting and Psychic types. They can be resisted by Colorless and Darkness, as well as Metal Pokémon since the Diamond and Pearl expansion set.
Generation I introduced the most Poison-type Pokémon of any generation, with 33, and Generation VI introduced the fewest Poison-type Pokémon, with two.
As of Generation VII, more than half of the Pokémon that have the Poison-type were introduced in Generation I.
Generation I introduced the most Poison-type moves of any generation, with eight, and Generation II introduced the fewest Poison-type moves, with only one.
In Generation I, the Poison type is super effective against Bug-type Pokémon, while the Bug type is super effective against Poison-type Pokémon. As such, this was the only different type match-up that was super effective against each other.