World 4 in Yoshi's Island DS takes place in the mountains of Yoshi's Island, becoming snowier and colder in the second half as Yoshi scales greater heights. In World 4-5, Baby Bowser encounters Yoshi and his party, and decides to join them on their adventure. However, this alliance is short-lived, as at the end of the world, Baby Bowser abandons the party as he attempts to go off with Kamek. World 4, like all other worlds in the game, has a total of ten levels; six regular, two hidden, and two bosses. The bosses in this world are Six-Face Sal and Big Guy the Stilted.

Level info[edit]

• 4-1: Rock 'n' Fall – This level takes place on the cliffs of Yoshi's Island. Yoshi needs to jump across rocks while avoiding getting crushed by ones coming from above.
• 4-2: High-Speed Cart Race – This level takes place on a high mountain. Yoshi uses a cart to progress through the level.
• 4-3: In the Clouds – This level takes place in the skies of Yoshi's Island where Yoshi has to bounce on clouds to progress though the level.
• 4-4: Six Face Sal's Fort – This level is inside a fortress filled with lava and Fangs, the boss of this level is Six Face Sal.
• 4-5: Friend or Foe? – This level introduces Baby Bowser who can be used to melt ice and light up dark places.
• 4-6: Slip Slidin' Away – This level is on a icy mountain and has a lot of Bumpties which Yoshi must avoid.
• 4-7: Teeth-Chattering Chill Zone – This level involves using the slippery ice as an advantage and as something to beware of, the latter parts of the level introduces Ski Yoshi.
• 4-8: Castle of Big Guy the Stilted – This level takes place in a Castle and involves using Baby Bowser as a shortcut to trigger things that normally require eggs, Big Guy the Stilted is the boss of the castle.
• Secret 4: Hurry and Throw! – This level is inside a castle where the screen autoscrolls in a circle; Yoshi has to run around and collect the three Number Balls to open the door to the next section, where Yoshi has to jump off of the heads of Koopa Paratroopas in the sky.
• Extra 4: Let There Be Light! – A level which begins in a dark fortress with Spikes and Bullet Bills, leading to a space section with Flatbed Ferries, Spinners, and more spikes.