Super Mario Bros. Wonder is the first Mario game to feature Kevin Afghani as the voice of both Mario and Luigi, replacing Charles Martinet, who announced his retirement from voice acting and shift to a brand ambassador position earlier in 2023.

While Afghani didn't announce his involvement until October 13, 2023, his presence in the game was leaked two days earlier on 4chan, when an anonymous user datamined a kiosk demo and leaked the game's voice cast, backing this up with images showing parts of the game that hadn't been publicly revealed yet. Because the cast list didn't state the voice actors' roles, users used process of elimination to determine who Mario's voice actor was, incorrectly guessing that it was Mick Wingert after assuming that Afghani was only voicing the Talking Flowers. In a statement sent to IGN, Wingert's agent refuted the claim that he was voicing Mario, and was later revealed to actually be the voice for the Talking Flowers.