World 1 is the first set of stages in Yoshi's Island DS. The Burt Bros. and Gilbert the Gooey are the bosses of this world. This world introduces Baby Mario and Baby Peach to the player.
 Brief Level Info
- Ba-dum BUM!: The first level in Yoshi's Island DS. It is very plain, with mostly basic level elements. Resembles Make Eggs, Throw Eggs.
- Hit the M Blocks!: This level introduces the player to M Blocks. Baby Mario has to hit them.
- Mario's Fleet Feet: Based around Baby Mario's dash ability, and the debut of the Super Big Tap-Tap.
- Castle of the Big Burt Bros.: The first castle of the game, containing the first boss, the Burt Bros.
- Catch the Breeze: The introduction of Baby Peach and her wind floating ability.
- Glide Guys Take to the Skies: A level containing wind currents, Glide Guys, Sluggers, Green Gloves and the very first Yoshi Helicopter.
- Baby Mario and Baby Peach: Dynamic Duo: This level is mostly spent switching between to two mentioned babies.
- Gilbert the Gooey's Castle: The final castle of World 1, with the second boss in the game, Gilbert the Gooey.