NES Ninja Gaiden:
Turn in all 50 scarabs at the item shop to unlock the old skool Ninja Gaiden (NES) for play at Han's Bar.
Arcade Ninja Gaiden:
Complete the game under any difficulty setting.
Ninja Dog Difficulty:
Die three times in a row in Chapter 1. Answer "Yes" when asked "Do you really give up the way of Shinobi?".
Hard Difficulty:
Have a completed Ninja Gaiden saved game on your hard drive. Or, complete the game on Ninja Dog or normal difficulty.
Very Hard Difficulty:
Have a completed Ninja Gaiden: Hurricane Pack 2 saved game on your hard drive. Or, complete the game on hard difficulty.
Master Ninja Difficulty:
Complete the game on Very Hard difficulty setting.
Costumes! Beat these missions/modes for alternate costumes:
| Ninja Dog or Normal difficulty | Comic |
| "Special" mission | Dead Or Alive |
| Hard difficulty | Red Muffler |
| Very Hard difficulty | Ryuken |
