Unlockable - Unlock mission cards | |
| M1 Clear Card | Complete mission 1 |
| M2 Clear Card | Complete mission 2 |
| M3 Clear Card | Complete mission 3 |
| M4 Clear Card | Complete mission 4 |
| M5 Clear Card | Complete mission 5 |
| All clear | Complete every mission |
Unlockable - "Complete" a mission | |
| In a mission, rescue every prisoner and collect every available item (the X-Ray scan card is useful for this) to get a golden "COMPLETE" sign over a mission on the map screen. | |
Unlockable - Get the boss cards | |
| When you are fighting a boss, you must destroy it very quickly to get its card (A message will appear on screen informing you that you have the card) To defeat the bosses quickly you must have lots of grenades and a special weapon (like the flame shot for the fourth boss) or use the Metal Slug if you can get it (Second, third and final boss) | |
Unlockable - Unlock the extra Dungeon mission | |
| In Mission 5, find and collect the dungeon card. Then complete mission 5 and go to the mission select screen and to the top left there is an extra mission called dungeon. | |
Unlockable - Ways to unlock prisoner cards | |
| Prisoner A Card | Rescue 10 prisoners |
| Prisoner B Card | Rescue 20 prisoners |
| Prisoner C Card | Rescue 30 prisoners |
| Prisoner D Card | Rescue 40 prisoners |
| Prisoner E Card | Rescue 50 prisoners |
| Prisoner F Card | Rescue 60 prisoners |
| Prisoner G Card | Rescue 70 prisoners |
| Prisoner H Card | Rescue 80 prisoners |
| Prisoner I Card | Rescue 90 prisoners |
| All saved | Rescue all prisoners |
Unlockable - How to unlock soldier cards | |
| Soldier A card | Kill 100 soldiers |
| Soldier B card | Kill 200 soldiers |
| Soldier C card | Kill 300 soldiers |
| Soldier D card | Kill 999 soldiers |
| Washout | Don't kill any enemies and complete a level. Just die as soon as you start a level. |
Unlockable - Unlock Decoration Card | |
| You need the "paper thin" card. Turn it on, then complete any mission. With paper thin turned on you will die with just one hit. The easiest way to get the decoration card is to complete mission 2, mainly because there is a Metal Slug at the near start of the level which is shielded, so if you can manage to get through the level with the Metal Slug it shouldn't be as difficult to get the card. | |
Unlockable - Unlock All cards card | |
| Collect all 99 cards in the game to get the final 100th "All cards" card. | |
Unlockable - Get Allen Jr's card | |
| In mission 5, find and kill Allen. (He has a large machine gun, throws grenades and will slash you with a knife if you get close and is different to any normal enemy) When you do kill him, he will drop a card. Collect it, then complete the level without dieing to keep the Allen Jr card. | |
Secret - Parachute route in mission 5 | |
| In mission 5, jump into the plane slug. Now as soon as you start the level proper, press L to crash the slug. You will eject and go onto a different route where you parachute down into the enemy docks. | |
