 | Mark Ruffalo als Dan Mulligan |
 | Keira Knightley als Gretta James |
 | Adam Levine als Dave Kohl |
 | Hailee Steinfeld als Violet Mulligan |
 | Catherine Keener als Miriam Hart |
 | James Corden als Steve |
 | Yasiin Bey als Saul |
 | Aya Cash als Jenny |
 | Maddie Corman als Phillis |
 | Karen Pittman als Business Woman |
 | Paul Romero als Bartender |
 | Andrew Sellon als Christian Father |
 | Ed Renninger als Barman |
 | Eric Burton als Singer Songwriter 2 |
 | Marco Assante als Marco |
 | Mary Catherine Garrison als Jill |
 | Jen Jacob als Dave Fangirl |
 | Rob Morrow als CEO |
 | Jennifer Li Jackson als Mim |
 | Ian Brodsky als Malcolm |
 | Shannon Walsh als Rachel |
 | David Abeles als Glen |
| Ann McGowan als Ballet Teacher |
| Ron Voz als Butler |
 | Cee Lo Green als Troublegum |
 | Kena Onyenjekwe als Troublegum Posse 1 - Rappa DD |
 | Harvey Morris als Troublegum Posse 2 - Phat Jimmy |
 | Terry Lewis als Troublegum Crew Member - Benson |
| Colin Love als Singing Basketball Player |
 | Jimmy Palumbo als Guy Shouting from Window |
 | Simon Delaney als Lawyer |
 | Danielle Brisebois als Singer |
 | Keen Ruffalo als Keen |
| Melissa Maria Gonzalez als Chris |
 | Nicholas Daniel Gonzalez als Zach |
 | David Pendleton als Homeless Man |
 | Madison Love als Singer Songwriter 1 |
| Joanna Mauer als On Camera Musician |
| Erik Detusch als On Camera Musician |
| Rich Mercurio als On Camera Musician |
| Emilie Cardinaux als On Camera Musician |
| Curtis Fowlkes als On Camera Musician |
| Emily Yarbourgh als On Camera Musician |
| Erin Benin als On Camera Musician |
| Alexis Sykes als On Camera Musician |
| Julia Bruskin als On Camera Musician |
 | Stacey Maltin als Young Girl |
 | Sama Fernands als Concert Attendee (uncredited) |
| John Carney | Writer |
| John Carney | Director |
| Gregg Alexander | Original Music Composer |
| Anne Goelz | Art Direction |
| Jeanne McCarthy | Casting |
| Anthony Bregman | Producer |
| Andrew Marcus | Editor |
| Tobin Armbrust | Producer |
| Stephanie DeCourcey | Casting |
| Chad Keith | Production Design |
| Yaron Orbach | Director of Photography |
| Andrea von Foerster | Music Supervisor |
| Matthew Sullivan | Music Supervisor |
| Arjun Bhasin | Costume Design |
| Shira Rockowitz | Co-Producer |
| Ian Watermeier | Co-Producer |
| Lauren Selig | Co-Producer |
| Sam Hoffman | Executive Producer |
| Molly Smith | Executive Producer |
| Tom Rice | Executive Producer |
| Ben Nearn | Executive Producer |
| Guy East | Executive Producer |
| Nigel Sinclair | Executive Producer |
| Marc Schipper | Executive Producer |
| Judd Apatow | Producer |
| Sam Hoffman | Unit Production Manager |
| Mariela Comitini | First Assistant Director |
| Maura Kelly | Second Assistant Director |
| Brian Smyj | Stunt Coordinator |
| Kris Moran | Set Decoration |
| Ludovic Littee | "A" Camera Operator |
| Scott Tinsley | First Assistant Camera |
| Andrew D. Schwartz | Still Photographer |
| Brian Carmichael | Video Assist Operator |
| Rebecca Breckel | Script Supervisor |
| Tod A. Maitland | Sound Mixer |
| James Baker | Boom Operator |
| Rob Harlow | Key Grip |
| Shawn Greene | Gaffer |
| Jennifer Crammer | Production Coordinator |
| Gina Herold | Art Department Coordinator |
| T.J. Horan | Leadman |
| Tommy Allen | Property Master |
| Richard Hebrank | Construction Coordinator |
| Drew Jiritano | Special Effects Coordinator |
| Yaneya Rovira | Wardrobe Supervisor |
| Margaret Moy | Costumer |
| Eileen Goh | Costumer |
| Cathryn Hunt | Costume Coordinator |
| Erin Hicks | Hair Department Head |
| Lair Paulsen | Key Hair Stylist |
| Louise McCarthy | Makeup Department Head |
| Joanna McCarthy | Key Makeup Artist |
| Steven Weisberg | Location Manager |
| J. Alex Finch | Second Second Assistant Director |
| Alexis Wiscomb | Post Production Supervisor |
| Suzana Peric | Music Editor |
| Erich Stratmann | Music Editor |
| Lewis Goldstein | Supervising Sound Editor |
| Lewis Goldstein | Sound Re-Recording Mixer |
| Max Greene | Dialogue Editor |
| Patrick Cicero | Dialogue Editor |
| Cate Montana | Supervising ADR Editor |
| Tom Ryan | Foley Editor |
| Sean Garnhart | Sound Effects Editor |
| Tom Ryan | Foley Recordist |
| Tom Ryan | ADR Recordist |
