Monkey Mask  -  Get the top five high scores in the Snake Vs. Ape mini-game to unlock the Monkey Mask.

Secret Theatre  -  Start a new game on Disc 1: Subsistence, then save the game. The Secret Theatre option will now be available on Disc 2: Persistence at the main menu.

Secret Camouflage room  -  Successfully complete both "New Game" types to unlock the Secret Camouflage room.

Control title screen  -  Press L3 to change the background pattern. Press R1 or R2 to control its speed. Press L1 or L2 to change the color of Snake and the soldier. Press R3 to change the screen's color. Press Triangle to turn the background black.

Motion capture model names  -  When the name of a character appears in parenthesis during an intermission sequence, press Circle. The name will change to the person that provided the motion capture actions for that character.

Camouflage Download  -  Save the game during Disc 1 to unlock the "Camouflage Download" option at the main menu on Disc 1.

Duel mode  -  Select the "I like MG3!" option when starting a new game to unlock Duel mode on Disc 2.

European Extreme  -  Select the "I like MGS3!" option when starting a new game to unlock the European Extreme.

All Snake vs. Monkey missions  -  To unlock all of the Snake vs. Monkey missions on Disc 2, first play Disc 1. When starting a new game on Disc 1 and are asked which Metal Gear Solid game you like, select option 4, "I like MGS!". When the game starts, save it as soon as you can. Take out Disc 1 and insert Disc 2. Go to Snake vs. Monkey and all of the missions should now be unlocked instead of having "?????" in their place. Doing this also unlocks the Demo Theater on Disc 1 and the Secret Theater on Disc 2, along with the Duel option on Disc 2.

Animals Camouflage  -  Defeat Ocelot to unlock the Animals Camouflage.
Cold War Camouflage  -  Defeat Volgin to unlock the Cold War Camouflage.
Fire Camouflage  -  Defeat The Fury to unlock the Fire Camouflage.
Hornet Stripe Camouflage  -  Defeat The Pain to unlock the Hornet Stripe Camouflage.
Moss Camouflage  -  Hold up The End to unlock the Moss Camouflage.
Snake Camouflage  -  Defeat The Boss to unlock the Snake Camouflage.
Spider Camouflage  -  Defeat The Fear to unlock the Spider Camouflage.

Stealth Camouflage  -  Shoot all the green frogs in the game to unlock the Stealth Camouflage. Alternately, successfully complete the game with no alerts. A good way to get the Stealth Camouflage with no alerts is, if you do get seen, immediately save the game and enable the "In-game reset" code to return to the title screen. Reload the game and you will begin at your last location with no alerts. Keep using this process until the end of the game in order to get the Stealth Camouflage on any difficulty setting.

The Sorrow's Camouflage  -  In the dream sequence where you face The Sorrow (at the stream with lightning and ghosts), walk all the way forward until you see The Sorrow's ghost hovering over his skeleton. Let him kill you while standing over his skeleton then press R2 when the screen reads "Game Over - Time Paradox" to access the Revival Pill. If done correctly, you should now have The Sorrow's Camouflage in your uniforms. The camouflage's special abilities eliminate all footstep noises from you. You can also drain enemy stamina in CQC holds and add it to your own.

Bandana in original MSX Metal Gear games  -  Successfully complete MSX Metal Gear or Metal Gear 2: Solid Snake to unlock the bandanna for that game. When equipped, the bandanna gives you infinite ammunition for all weapons.

Boss Time Trial in original MSX Metal Gear games  -  Successfully complete MSX Metal Gear or Metal Gear 2: Solid Snake and save the game when prompted to unlock the "Boss Time Trial" option at the main menu for the corresponding MSX game.

EZ gun  -  Play the game on the Very Easy difficulty setting to unlock the EZ gun, a silenced tranquilizer weapon with infinite ammunition.

Mosin Nagant tranquilizer sniper rifle  -  Defeat The End with the Mk22 to get the Mosin Nagant tranquilizer sniper rifle.

Play as Reiko and Dixie  -  Accumulate 50 hours of online game play time to unlock Reiko and Dixie from Rumble Roses. Alternately, host an online game.

Alternate title screen  -  Successfully complete the game to have Snake wear an eye patch during the CQC fights with the Russian guard at the title screen.

Finding The End  -  When battling The End, go to the map screen press Up(2), Down(2), Left, Right, Left, Right, Square, Triangle to see him on the map.

High score in Duel mode  -  A good way to get a high score is to choose one weapon and kill the Boss as fast as possible. It also helps if you collect ammunition for your weapons before defeating the Boss. The shorter the time and more ammunition you carry, the higher the score. You will not lose points for damage or using your medical items.

In-game reset  -  While playing the game, hold L1 + L2 + R1 + R2 + Select + Start to return to the title screen.