The iron balls are objects found throughout Pikmin 3 that serve as an interactable obstacle, much like the cardboard boxes. They are very plain metallic-gray orbs with "20 weight" inscribed on them. As the number would imply, 20 Pikmin are needed to push them.
Iron balls are always placed at the tip of a slope, so they will rush down a fixed path once the Pikmin have set one in motion. With its momentum and weight, it will break open walls the Pikmin could not have torn down themselves. This opens entrances and exits to other parts of an area. Creatures in the ball's path will be killed, allowing the player to defeat enemies in some rare cases, but Pikmin (that aren't Rocks) are more likely to be crushed if the player does not pay attention. As such, it is not advised to have more than 20 Pikmin charge at a ball, as some of them may get in front of it while attempting to find a spot to push on. Because there is not enough surface area on the object for 20 Pikmin to push it, some Pikmin will go behind other ones and push them instead.
- One is atop the slope where the Yellow Onion is. When it rolls down, it destroys the blockade on the cave's main exit.
- Another ball serves as the "nose" on the President snowman figure. When pushed out, it rolls until it destroys the blocked entrance to the cave with the Pyroclasmic Slooches.
- The room with the bridge and Arachnode has the final ball in story mode. When pushed, it rolls down a slope and destroys a crystal wall down below.
- One stands in the same location in Story Mode. It is next to a Whiptongue Bulborb and beyond it are many Dwarf Bulborbs.
- Another is near the area where Brittany starts and 2 Orange Bulborbs, and destroys a path of Bulborbs and a crystal wall.
Arachnode web • Bloominous Stemple • Bodies of water • Boulder • Bouncy Mushroom • Bridge (fragments, hay) • Burgeoning Spiderwort mold • Cardboard box (tin box) • Climbing stick • Clog • Cobblestone block • Conveyor belt • Crystals • Dirt block • Dirt mound • Electrical wire • Electrode • Fire geyser • 24x24px Flames • Flukeweed (dam) • Gas pipe • Gates and walls • Geyser • Hydroe bramble • Iron ball • Iron block • Liftable rock • Lily pad • Paper bag • Pulley rock • Seesaw blocks (elevator platforms) • Spotcap and Kingcap • Trowel • Tunnel