Mario, Luigi, and Princess Peach have traveled to Yoshi's Island in Dinosaur Land for a well-deserved vacation. Shortly after arriving, however, Princess Toadstool disappears! Mario and Luigi search desperately for her, but to no avail. Finally, at the edge of the island, they come across a mysterious egg. While they're taking a good, long look at the egg, it suddenly hatches and out pops a little dinosaur named Yoshi, who tells Mario and Luigi his sad tale. "A group of turtles appeared here in Dinosaur Land and used magic to trap my friends inside eggs. Those turtles are really tough---they even trapped me when I came to help out my pals. Will you help me free my friends?" Monstrous turtles? Surely, this is the work of Bowser, king of the Koopas. He and his henchmen must be behind Peach's disappearance, too! Now the Mario brothers must team up with Yoshi to free the princess and the other dinosaurs and start on a whole new adventure.