After rescuing Princess Peach (Anya Taylor-Joy) and defeating Bowser (Jack Black), Mario (Chris Pratt) and Luigi (Charlie Day) face their newest challenge: Bowser Jr. (Benny Safdie).

The brothers team up with a newly hatched Yoshi (Donald Glover) and set off across the Galaxy to stop Bowser Jr. from freeing his father. Along the way, they make new friends, Rosalina (Brie Larson) and Fox McCloud (Glen Powell), while reuniting with familiar faces like Toad (Keegan-Michael Key). Together, they embark on a cosmic adventure full of excitement, friendship, and heroism.