World 1 is the first world in New Super Mario Bros. Wii, consisting of six levels, a fortress, a castle and a boss, three special stages - accessible by entering the Mushroom Houses - as well as housing Princess Peach's Castle. There are three special stages, two reds and one gold; the two reds occurring upon completion of World's 1-2 and 1-4, and the Gold Mushroom House occurring upon completion of World 1-3.
Levels
| World | Unlocks upon completion | Secret exit? |
|---|---|---|
| 1-1 | World 1-2 | No |
| 1-2 | World 1-3 Red Mushroom House |
No |
| 1-3 | World 1-Fortress Gold Mushroom House |
Yes (Leads to 1-Cannon) (It brings you to World 5) |
| 1-Fortress | World 1-4 | No |
| 1-4 | Enemy Area World 1-5 World 1-6 Red Mushroom House |
No |
| 1-T | 3 Mushrooms | No |
| 1-5 | World 1-Castle | No |
| 1-6 | World 1-Castle | No |
| 1-Castle | World 2-1 | No |
