- Anthony Kiedis: Vocals, composer
- Josh Klinghoffer: Guitar, bass, piano, backing vocals, composer
- Flea: Bass (1-11, 13), piano (2, 12), trumpet (12), composer
- Chad Smith: Drums, composer

- Mauro Refosco: Percussion (6, 7)
- Jeremy Levy: Score preparation
- Sharon Jackson: Violin
- Peter Kent: Violin
- Briana Bandy: Viola
- Armen Ksajikian: Cello
- Daniele Luppi: String arrangements, string conductor
- Chris Tedesco: String quartet contractor
- Beverly Chitwood: Choir/chorus, soloist
- Anna Waronker: Vocals
- Alexx Daye: Choir/chorus
- David Loucks: Choir/chorus
- Kennya Ramsey: Choir/chorus
- Matthew Selby: Choir/chorus
- Loren Smith: Choir/chorus
- Greg Whipple: Choir/chorus

- Elton John: Piano, composer (6)
- Bernie Taupin: Composer (6)

- Brian Burton "Danger Mouse": Producer, organ, instrumentation, mellotron, composer (1)
- Kennie Takahasi: Recording engineer
- Greg Fidelman: Pre-production engineer
- Chris Warren: Pre-production engineer
- Andrew Scheps: Pre-production engineer
- Sam Petts-Davies: Mixing engineer
- Nigel Godrich: Mixing, programming
- John Armstrong: Mixing assistant
- Todd Monfalcone: Assistant engineer
- Stephen Marcussen: Mastering

- Red Hot Chili Peppers: Art direction
- Kevin Peterson: Cover art
- Alex Tenta: Design, layout
- Steve Keros: Photography