The pair will be joining the previously announced Ken Jeong as Dynomutt and Kiersey Clemons as Dee Dee Sykes.
Scoob! is written by Matt Lieberman (The Addams Family) and directed by Tony Cervone (Space Jam).
The film will follow the mystery-solving group as they must team up with other characters from the Hanna-Barbera universe to save the world from supervillain Dick Dastardly.
Oscar nominee Mark Wahlberg (The Fighter, The Departed) and Golden Globe nominee Jason Isaacs (The State Within, The OA) have also been cast in the roles of superhero Blue Falcon and villain Dick Dastardly.