A version of Metal Gear was released for mobile phones in Japan on August 18, 2004.
The game is based on the original MSX2 version, but includes several additional features and changes.
* New Easy mode - Player can choose to play with the original MSX2 version's difficulty or with an easier difficulty setting.
* Boss Survival mode - After clearing the game once (regardless of difficulty setting), a new game mode in which the player fight against all of the main game's bosses. The player will be awarded with a title based on their clear time (as well as in the main game).
* Infinite Bandana - A hidden item which becomes available to the player after clearing the game once on either difficulty settings. Like the bandana featured in Metal Gear Solid and Metal Gear Solid 2, this will conserve the player's ammunition to the present amount while firing.
* Rewritten Script - The Japanese language script has been rewritten to include hiragana and kanji, in addition to romaji and katakana.
*Name Changes - Three of the game's bosses got their names changed in the mobile phone version.
* Shoot Gunner was changed to Shotmaker.
* TX-11 Cybernoid "Arnold" Twins was changed to Bloody Brad.
* Coward Duck was changed to Dirty Duck.
