 Jacob TremblayOrion (voice) | Orion (voice) |
 Paul Walter HauserDark (voice) | Dark (voice) |
 Angela BassettSweet Dreams (voice) | Sweet Dreams (voice) |
 Colin HanksAdult Orion (voice) | Adult Orion (voice) |
 Natasia DemetriouSleep (voice) | Sleep (voice) |
 Golda RosheuvelUnexplained Noises (voice) | Unexplained Noises (voice) |
 Nat FaxonInsomnia (voice) | Insomnia (voice) |
 Aparna NancherlaQuiet (voice) | Quiet (voice) |
 Ike BarinholtzLight (voice) | Light (voice) |
 Carla GuginoOrion's Mom (voice) | Orion's Mom (voice) |
 Matt DellapinaOrion's Dad (voice) | Orion's Dad (voice) |
 Nick KishiyamaTycho (voice) | Tycho (voice) |
| MMia Akemi BrownHypatia (voice) | Hypatia (voice) |
 Shannon Chan-KentAdult Hypatia (voice) | Adult Hypatia (voice) |
 Jack FisherRichie Panici (voice) | Richie Panici (voice) |
 Werner HerzogNarrator (voice) | Narrator (voice) |
 Sky AlexisLisa (voice) | Lisa (voice) |
 Hira AmbrosinoWoman at the Drive-In (voice) | Woman at the Drive-In (voice) |
| YYoshi AndoMan at the Drive-In (voice) | Man at the Drive-In (voice) |
| LLarisa AsuajeMrs. Spinoza (voice) | Mrs. Spinoza (voice) |
 Sean CharmatzIrene's Boss / Cucumber Dentist / Soda / Insomnia Guy 1 (voice) | Irene's Boss / Cucumber Dentist / Soda / Insomnia Guy 1 (voice) |
 Walt DohrnStray Cat / Insomnia Guy 2 (voice) | Stray Cat / Insomnia Guy 2 (voice) |
 Ren HanamiAdult Sally (voice) | Adult Sally (voice) |
 Amy HillIrene (voice) | Irene (voice) |
| AAlyssa LeeIrene's Daughter / Insomnia Girl (voice) | Irene's Daughter / Insomnia Girl (voice) |
| NNoah McCownScared Child (voice) | Scared Child (voice) |
| SShino NakamichiSally (voice) | Sally (voice) |
 Aliki TheofilopoulosIrene's Coworker / Mom / Juice Box / Insomnia Teacher (voice) | Irene's Coworker / Mom / Juice Box / Insomnia Teacher (voice) |
 Toru UchikadoInsomnia Man (voice) | Insomnia Man (voice) |
 Benjamin PlessalaAdditional Voices (Voice) | Additional Voices (Voice) |
