| Jared Padalecki | Sam Winchester |
| Jensen Ackles | Dean Winchester |
| Misha Collins | Leviathan |
| Jim Beaver | Bobby Singer |
| Mark Pellegrino | Lucifer |
| Kim Rhodes | Sheriff Jody Mills |
| Cameron Bancroft | Dr. Gaines /
Leviathan |
| Benito Martinez | Edgar /
Leviathan |
| Olivia Steele Falconer | Annie /
Leviathan
(as Olivia Steele-Falconer) |
| Lori Triolo | Head Nurse /
Leviathan |
| Patti Allan | Madeline Hackett |
| Michael Rys | Hospital Administrator |
| Isaiah Adam | Forensics Tech
(as Hamza Adam) |
| Justin Breault | EMT |
| Travis Nelson | Swim Student #1 /
Leviathan |
| France Perras | Receiving Nurse |
| Andrew MacFarlane | Scott |
| Jason Duiven | Gym Student #2 /
Leviathan |