What it does
Poison Jab is a Poison-type physical move with a chance to inflict Poison on hit. Poison-type attacks deal super-effective damage to Fairy-type Pokémon, which is the primary coverage reason to run this move — Fairy support is common in doubles, and Poison-type physical attackers address that threat directly.
Poison ticks for HP each turn. In doubles, matches tend to run shorter than in singles, so poison's cumulative damage is less decisive — but against support Pokémon that run recovery items or healing abilities, the ongoing damage keeps pressure building after the initial hit.
Contact classification applies — expect Rocky Helmet or Rough Skin recoil when hitting Pokémon that carry them.
Who runs it
Toxicroak uses it at 56%. Poison/Fighting type means Poison STAB, and the Fairy coverage is exactly what a Fighting/Poison attacker needs. Dry Skin heals HP in rain, so in rain-heavy environments Toxicroak has two recovery sources.
Ariados (Bug/Poison) uses it as the primary Poison-type physical attack alongside its web and status support tools.
Arbok is pure Poison-type — Poison Jab delivers STAB coverage against Fairy targets.
Araquanid (Water/Bug) occasionally uses it for Fairy-type coverage off its physical Attack.
How to use it
In doubles, the clearest scenario is: the opponent has a Fairy-type Pokémon and your Poison-type physical attacker is in the match. Hit it. No additional judgment needed.
The poison chance is secondary upside. Think of Poison Jab as 'Poison-type physical damage that sometimes poisons' rather than 'a status move that also deals damage.' The damage is the plan; the status is a bonus.
Steel-type Pokémon are immune to Poison-type moves — Poison Jab does zero damage. Poison-type Pokémon resist them (×0.5) and cannot be poisoned, but they still take damage.
Tips & strategy
Fairy coverage is the core reason to choose Poison Jab over other coverage options for a Poison-type physical attacker. STAB plus super-effective versus Fairy gives a Pokémon like Toxicroak a very clean damage output against the Fairy targets it's matched up against.
Poison has extended value when the target's healing item has been used up earlier in the match. If Lum Berry was consumed by a prior status condition (paralysis, sleep), the target has no way to clear the poison, and the ongoing damage accumulates without an answer.