 | Lewis MacDougall als Conor |
 | Liam Neeson als The Monster (voice) |
 | Sigourney Weaver als Grandma |
 | Felicity Jones als Mum |
 | Toby Kebbell als Dad |
 | Ben Moor als Mr. Clark |
 | James Melville als Harry |
 | Oliver Steer als Sully |
 | Dominic Boyle als Anton |
 | Jennifer Lim als Miss Kwan |
 | Max Gabbay als Steven |
| Joe Curtis als Peter |
 | Morgan Symes als Lawyer |
| Max Golds als 5-Year-Old Connor |
 | Frida Palsson als Lily's Mum |
 | Wanda Opalinska als Female Nurse |
| Patrick Taggart als Teacher |
 | Lily-Rose Aslandogdu als Lily |
 | Geraldine Chaplin als The Head Teacher (uncredited) |
 | Jake Talbot als Rollercoaster Boy (uncredited) |
| Lee Bolton als Rollercoster Rider (uncredited) |
| Garry Marriott als Paramedic (uncredited) |
| Patrick Ness | Screenplay |
| J. A. Bayona | Director |
| Patrick Ness | Novel |
| Ravi Bansal | Art Direction |
| Álvaro Augustin | Executive Producer |
| Sandra Hermida | Co-Producer |
| Dídac Bono | Art Direction |
| Sarah Wheale | Line Producer |
| Patrick Wachsberger | Executive Producer |
| Stephen Noble | Costume Design |
| Siobhan Dowd | Idea |
| Shaheen Baig | Casting |
| Pilar Revuelta | Set Decoration |
| Patrick Ness | Executive Producer |
| Eugenio Caballero | Production Design |
| Bernat Vilaplana | Editor |
| Jeff Skoll | Executive Producer |
| Ghislain Barrois | Executive Producer |
| Mitch Horwits | Executive Producer |
| Bill Pohlad | Executive Producer |
| Jaime Anduiza | Art Direction |
| Jonathan King | Executive Producer |
| Fernando Velázquez | Original Music Composer |
| Enrique López Lavigne | Executive Producer |
| Belén Atienza | Producer |
| Óscar Faura | Director of Photography |
| Jaume Martí | Editor |
| Sandra Hermida | Executive Producer |
| Tom Holland | Stand In |
| Steve Joberns | Thanks |
| Félix Bergés | Visual Effects Supervisor |
| Marese Langan | Makeup Designer |
| Marese Langan | Hair Designer |
| Pau Costa | Special Effects Supervisor |
| Oriol Tarragó | Sound Designer |
| David Martí | Makeup Effects |
| Montse Ribé | Makeup Effects |
| Marc Bech | Sound Effects Editor |
| Laura Díez Mora | Dialogue Editor |
| Wasselena Bilak | Visual Effects Coordinator |
| Peter McDonald | Visual Effects Supervisor |
| Esther Mestres | Second Assistant "C" Camera |
| Layla Merrick-Wolf | Casting Associate |
| Maryllis Gonzalez | Production Accountant |
| Víctor Martí | Post Production Supervisor |
| Debora Witte | Electrician |
| Carmen Romero | Extras Casting |
| Anita Primett | Studio Teacher |
| Joseph Díaz | Concept Artist |
| Sean Sevestre | Concept Artist |
| Albert Carreras | Camera Operator |
| Yousef El Awage | Epk Camera Operator |
| José Haro | Still Photographer |
| Marc Estrugo | Set Designer |
| Florian Müller | Set Designer |
| Jose Ruiz | Foley Editor |
| Edward Botham | Second Assistant Camera |
| Cristina Malillos | Makeup Effects |
| Jesus Espin | Third Assistant Director |
| Paul Lowe | Stunt Double |
| Mónica Sánchez | Second Assistant Director |
| Elizabeth Himelstein | Dialogue Coach |
| Sarah Shepherd | Dialect Coach |
| Goyo Gámez | Unit Manager |
| Albert Ribas | Dialogue Editor |
| Ramón Sánchez | Steadicam Operator |
| Kelly Zampogna | Makeup Artist |
| Quim Vives | Still Photographer |
| Queralt González | Assistant Editor |
| Andrey Ryabovichev | Concept Artist |
| Don Hoffman | Sound Re-Recording Mixer |
| Kyle D. Krajewski | ADR Mixer |
| Jordi Florensa | First Assistant Camera |
| Celine Gravez | Second Assistant Camera |
| Víctor Sarasa | Electrician |
| Lyndsey Haluszczak | Assistant Production Coordinator |
| Margarita Huguet | Unit Production Manager |
| Fernando Trullols | First Assistant Director |
| Tiger Rudge | Stunts |
| Miquel Auguet | Second Assistant Camera |
| Javier González Leonardo | Key Grip |
| José Luis Rodríguez | Gaffer |
| Jaume Martí | Post Production Supervisor |
| Jason Bond | Property Master |
| Abner Marín | Sculptor |
| Manuel Carrión | Foley Artist |
| Srinivas Janapati | Visual Effects Coordinator |
| Guillem Huertas | First Assistant "A" Camera |
| Jaime Gutiérrez Domínguez | Orchestrator |
| Eugenio Mira | Second Unit Director |
| Ian van Temperley | Stunt Coordinator |
| Alberto Bernad | VFX Editor |
| Inés Font | Post Production Coordinator |
| Patricia Johnson | Unit Publicist |
| Ruben Goldfarb | Second Assistant Director |
| Jan Zalar | Second Assistant Director |
| Ariel Margolis | Property Master |
| Thomas Barrera | Camera Trainee |
| Oriol Busquets | Camera Operator |
| David Valldepérez | Camera Operator |
| Ana Charte | Assistant Editor |
| Marcel Cifré | VFX Editor |
| Glòria Blanes | Script Supervisor |
| Josué Corral | Assistant Production Manager |
| Anna Capdevila | Third Assistant Director |
| Kieran O'Neal | Floor Runner |
| Ainara Castro | Visual Effects Producer |
| Cuco Usín | Stunt Coordinator |
| Martí Albert | Sound Effects Editor |
| Geraint Hixson | Visual Effects Coordinator |
| Jen Rooks | Production Coordinator |
| Marc Rial | Second Assistant Director |
| Javier López Antía | Assistant Property Master |
| Richard Rowntree | Greensman |
| Emma Saunders | Graphic Designer |
| Shaun Mills | Boom Operator |
| Marc Orts | Sound Re-Recording Mixer |
| Chus Lucas | Stunt Double |
| Anna Aguilà | Costume Supervisor |
| Ferran Domenech | Visual Effects Supervisor |
