“Luigi, I found this cap in front of the castle a little while ago. You must have dropped it. If you want to become a full-fledged hero like your brother, you can't be so careless!”
—Toad, Super Mario 64 DS
with its signature green "L" emblem.
Luigi's Cap is one of Luigi's important pieces of clothing. Like his brother, Luigi has worn the hat since he was a baby.
Luigi's hat color was taken from the Shellcreeper's palette to distinguish Mario from Luigi. The hat was made green with a green "L" emblem, but it was white on Super Mario Bros. and Super Mario Bros: The Lost Levels.
In Super Mario Bros. 2, Super Mario Bros. 3, and Super Mario World, the tip of the cap had been changed to black instead of its usual green. This happened for Mario's cap as well. However, after this game, Luigi's cap reverted to having a green tip.
In the Mario Kart games Mario Kart 64 and Mario Kart Wii, in the Luigi's Circuit (Luigi's Raceway in Mario Kart 64) courses, giant versions of Luigi's cap can be seen on top of the grandstands.
In Super Mario 64 DS, Luigi's hat was used to shape-shift into Luigi if the player was either Mario, Wario, or Yoshi. In the same game, Luigi is affected in the same way as Mario and Wario if his hat is lost. Luigi's defense and attack sharply decline while his hat is absent from his head. If the player gets the hat back, Luigi's attack and defense revert to normal. Until Luigi is unlocked, it only appears in Big Boo's Haunt, on any star except the first one.
In the Mario & Luigi series, the "L" on Luigi's cap is black. Mario's cap was changed in the same way. In Dream Team, they are the usual green and red.
In Super Paper Mario, when Luigi is reverted to Mr. L, his hat is slightly changed, with the white on his hat being turned to black and the "L" in the middle being turned backwards.
- Luigi's Cap is an item in Nintendogs that the player's dog can wear.
- In Animal Crossing: City Folk, and later New Leaf, there is a headgear item resembling Luigi's cap which the player's avatar can wear. The item is called "li'l bro's hat", in reference to Luigi being the younger brother of Mario.
- Baby Luigi's cap is on-purposely made larger, so it appears it was too big to wear when he was a baby.
- On the North American and European box art for Mario Kart: Double Dash!!, the "L" on Luigi's cap is backwards. This was likely a mistake by the graphic designer.