This story begins with a letter Mario receives from Princess Peach. In it she tells him that it is the Star Festival, and that he hasto go with her to the castle to see the stars from of it. Midway, the Toads celebrate.
With harmony this festival. On his way, Mario meets the Flash Master, who is lost. That's why he helps Mario in the adventure of him teaching her the spinning technique.

Mario continues to Peach's Castle. When he is already near the Castle, he watches as the Castle and the Mushroom Kingdom are invaded by Bowser, a giant Bowser and more powerful than ever, since he stole the power of the Stars and with this Great Power, he wants to create his galaxy in the center of the Universe.

where he will rule it together with Peach and his son, Bowser Jr.. Bowser tells Mario all his plans and takes Peach, running away from the place. Mario goes to the entrance of the Castle, where some sparkles identify the Flash Master that he
Mario with him, and they create a Star Ring, which with it Mario flies directly to the Sidereal Gardens Galaxy, where Mario has to complete his first mission, and beat his first boss to get the first Star of the game. After getting the Star, Mario lands on a small planet, flying into space, where he meets Star.

Mario tells him what happened and Star agrees to help him rescue Peach in exchange for him getting the Stars for the Spacecraft. Mario has to travel to the 6 Worlds, completing the missions and recovering Stars. To get to Castle of World six, where he arrives to face Bowser and thus save Princess Peach. And technically the affair has finished. But not one hundred percent, for this, he has to get the two hundred forty two Stars of the game, including green stars and kites. There is also an unlockable secret, that by getting all two hundred forty two stars in the game, Rosalina will be available in the Spaceship, thanking you.