The Iron Ball halves the holder's Speed and makes it grounded. Due to being grounded, it becomes susceptible to damaging Ground-type moves; Rototiller; Arena Trap; the entry hazards Spikes, Toxic Spikes and Sticky Web; and terrain, even if it is Flying-type, has the Ability Levitate, or is under the effect of Telekinesis or Magnet Rise.
If held by a Flying-type Pokémon, it takes damage from Ground-type moves as if Ground-type moves dealt 1× damage to pure Flying-type Pokémon.
Even if the holder has Klutz or is affected by Embargo, its Speed is still halved by the Iron Ball.
Generation V onward
If held by a Flying-type Pokémon, it takes 1× damage from Ground-type moves, regardless of its other types. This does not apply during Inverse Battles or if the holder is grounded by any other effect.
All of the effects of the Iron Ball are negated by Klutz, Embargo, and Magic Room.
||A Pokémon hold item that cuts Speed. It makes Flying-type and levitating holders susceptible to Ground moves.
|A Pokémon held item that cuts Speed. It makes Flying-type and levitating holders susceptible to Ground moves.
|An item to be held by a Pokémon. It lowers Speed and allows Ground-type moves to hit Flying-type and levitating holders.
||An item to be held by a Pokémon. It lowers Speed and allows Ground-type moves to hit Flying types and holders that are levitating.
This is the appearance of the Iron Ball in the Sinnoh Underground.