Each version of the game has unique codes and passwords. The Konami Code does not work in any version of this game.

These are codes for the 1992 game known as

1. Contra III: The Alien Wars
2. Contra Spirits
3. Super Probotector: Alien Rebels

Thirty Lives (Japanese version)

On the title screen, press Down Dpad, Down Dpad-Right Dpad, Right Dpad, and Start Button (the Hadoken command: ) in one smooth motion. If done correctly, you will hear the death scream of your character and you will begin the game with thirty lives. This works only in the Japanese version (Contra Spirits).

Stage Select (Japanese version)

On the title screen, press Down Dpad, Down Dpad-Left Dpad, Left Dpad, and Start Button (the Hurricane Kick command: ) in one smooth motion. If done correctly, you will hear an alien shriek and you can now choose which stage to the begin the game at. This works only in the Japanese version (Contra Spirits).

Sound Check Mode (Japanese version)

On the title screen, press Right Dpad, Down Dpad, Down Dpad-Right Dpad, and X Button (the Dragon Punch command: ) in one smooth motion. If done correctly, you will hear a noise and be taken to the Sound Check Mode, where you can listen to any of the game's sound effects and music. This works only in the Japanese version (Contra Spirits).

These are codes for the 1994 game known as

1. Contra: The Alien Wars
2. Contra Spirits

Passwords

Unlike the original version, the Game Boy port had a password system allowing you to start at any level.

1. B32R: Stage 1 with infinite lives
2. 3KNT: Stage 2
3. MDWH: Stage 3
4. 2S3W: Stage 4
5. 1Z5C: Stage 5
6. F5F5: Stage 5 with Flamethrower, extra lives and bombs
7. H2F2: Stage skip
8. BIER: Secret stage

These are codes for the 2002 game known as

1. Contra Advance: The Alien Wars EX
2. Contra: Hard Spirits
3. Contra Advance

Passwords

The Game Boy Advance port also had a password system, though more complex than the Game Boy version.

Stage 2

1. 11111N TYLH1Z FCS5H1: Novice mode
2. 111111 TYLH1S 35MYH1: Normal mode
3. Y4HC1B L5P212 34ZWF1: Normal mode with 99 lives

Stage 3

1. 111113 TYLH1W BHZXZ1: Novice mode
2. 11111H TYLH1X QTTH1B: Normal mode
3. WXJD1Z JHSJ1Q KKNCY1: Normal mode with 99 lives

Stage 4

1. 11111B TYLH1T XLGHSB: Novice mode
2. 11111J TYLH1Z MY1RSB: Normal mode
3. ZWJF1J MGSL1B GP3LQB: Normal mode with 99 lives

Stage 5

1. 11111V TYLH13 2D21LC: Normal mode
2. G3421N TDN51N C3BV2C: Normal mode with 99 lives

Stage 6

1. 11111M TYLH1V CFDJDD: Normal mode
2. W3MJ1S J4VP1N YY24BD: Normal mode with 99 lives

Psycho Cycler

1. Japanese name: Hell Riders (ヘルライダース Heruraidaasu)
2. European name: Hellriders

"High Speed Tank Booby"

1. Japanese name: High Speed Tank Booby (高速戦車ブービー号 Kousoku Sensha Buubii Gou)

"Sensor Arm"

1. Japanese name: Sensor Arm (センサーアーム Sensaa Aamu)

"Fierce Cannon"

1. Japanese name: Fierce Cannon (強烈砲台 Kyouretsu Houdai)

"Walking Bipedal Cannon"

1. Japanese name: Tetranducker (テトランダッカー Tetorandakkaa)
2. European name: Tetandakker

Slash

1. Japanese name: Rocket Ninja Sasaki (ロケット忍者ササキ Roketto Ninja Sasaki)
2. European name: Rocket Ninja Sasaki

Battleship

1. Japanese name: Anti-Contra Battleship Dodriguez (対魂斗羅戦艦ドドリゲス Tai Kontora Senkan Dodorigesu)
2. European name: Anti-Contra Sergeant Dodoriguez

"Alien Scorpions and Alien Scorpion Generators"

1. Japanese name: Oggies and Oggie Generators (オギー＆オギージェネレーター Ogii to Ogii Jenereetaa)

Scorpabellum

1. Japanese name: Top Secret Experimental Creature Anthell (極秘実験生物アントヘル Gokuhi Jakken Seibutsu Antoheru?)

"Humanoid Aliens"

1. Japanese name: Ogre-Faced Beast Orlean (鬼頭獣オーリアン Kitou Juu Oorian)

"Alien Mouth and Mouth spawns"

1. Japanese name: Ultra Preying Beast Wadder (超猛獣ワーダ Chou Moujuu Waada?) and Poisonous Insect Gell (毒々虫ゲル Dokudokuchuu Geru)
2. European name: Ultra-wild Animal Wadder

"Facehuggers and Facehugger Breeders"

1. Japanese name: Evil Insect Buggers (把妖虫バッカー Hayouchuu Bakkaa?) and Evil Eggrons (妖卵エグロン Youran Eguron)

Para-Slug

1. Japanese name: Uranian Devil Dragon Java (天王鬼龍神ジャバ Tennou Ki Ryuujin Jaba?) and Ogre-faced Beast Bandles (鬼頭獣バンドル Kitou Ju Bandoru)
2. European name: Jappa

"Giant Alien Heart"

1. Japanese name: Evil Heart of the Uranian Beast Gomera Mosking (天王創魔心ゴメラモスキング Tennou Sou Mashin Gomera Mosukingu)
2. European name: Gomeramos King

"Golden Beast"

1. Japanese name: Shadow Beast Kimkoh (陰獣キムコウ Injuu Kimukou)
2. European name: The Fearsome Beast Kimkoh

Vicious Slave Hawk

1. Japanese name: Metal Alien (メタルエイリアン Metaru Eirian)
2. European name: Metal Alien

His American name is a mistranslation of "Slave Beast Taka", which is the name of the giant turtle boss from Area 1.

Jagger Froid

1. Japanese name: Uranian Beast Gava (天王鬼ギャバ Tennouki Gyaba)
2. European name: Uranian Devil Gappa

"Alien Brain"

1. Japanese name: Living Brain Organism Searle (頭脳生命体サール Zunou Seimeitai Saaru)

"Armored Alien Brain"

1. Japanese name: Six Men Feromedos (フェロメドス六人衆 Feromedosu Rokuninshuu)