- Dee Bradley Baker
- Numbuh 4 - Wally Beatles / Mr. Fibb / Toilenator / Joaquin / Tommy Gilligan / Delightful Children from Down the Lane / Additional Voices (voice)
- Ben Diskin
- Numbuh 1 - Nigel Uno / Numbuh 2 - Hoagie P. Gilligan Jr. / Numbuh 101 - Matthew / Delightful Children from Down the Lane (voice)
- Cree Summer
- Numbuh 5 - Abigail 'Abby' Lincoln / Cree Lincoln / Delightful Children from Down the Lane (voice)
- Lauren Tom
- Numbuh 3 - Kuki Sanban
- Ogie Banks
- Sector Z Numbuh 0.1 - Bruce
- Jeff Bennett
- Mr. Boss / Mr. Fizz / Benedict Wigglestein (voice) (as Jeff Glen Bennet)
- Cam Clarke
- Additional Voices
- Grey Griffin
- Crazy Old Cat Lady / Gramma Stuffum (voice) (as Grey DeLisle)
- Jennifer Hale
- Numbuh 86 - Francine 'Fanny' Fulbright / Numbuh 363 - Harvey McKenzie / Computer (voice)
- Mark Hamill
- Stickybeard
- Jason Harris
- Chad Dickson
- Janice Kawaye
- Numbuh 83 - Sonya / Numbuh 84 - Lee (voice)
- Tom Kenny
- Knightbrace / Chester / Mr. Wink / Sector Z Numbuh 0.2 - David / Additional Voices (voice)
- Maurice LaMarche
- Father
- Matt Levin
- Numbuh 60 - Patton Drilovsky
- Rachael MacFarlane
- Numbuh 362 - Rachael T. McKenzie / Sector Z Numbuh 0.3 - Ashley (voice)
- Candi Milo
- Additional Voices
- Daran Norris
- Count Spankulot / Janitor (voice)
- Neil Ross
- Grandfather
- Frank Welker
- Monty Uno
- Dave Wittenberg
- Numbuh Zero / Sector Z Numbuh 0.4 - Lenny (voice)
