Will Ferrell as Sherlock Holmes

John C. Reilly as Dr. John Watson

Rebecca Hall as Dr. Grace Hart

Kelly Macdonald as Mrs. Martha Hudson

Rob Brydon as Inspector Lestrade

Lauren Lapkus as Millie

Pam Ferris as Queen Victoria

Ralph Fiennes as Prof. James Moriarty / Jacob Musgrave

Adam Scherr as Brawn

Kieran O'Brien as PC Smalls

Noah Jupe as Doxy

Bella Ramsey as Flotsam

Colby Mulgrew as Haybag

Scarlet Grace as Pickle

Billy Jenkins as Mud Fog

Michael Culkin as The Judge

Jana Pérez as Lestrade's Wife

Wolf Roth as Sigmund Freud

Nathan Osgood as Mark Twain

David Shackleton as Albert Einstein

Paul Cassidy as Charlie Chaplin

Ben Lee as Houdini

Bronson Webb as Jonathan Nightingale

Jamie-Rose Monk as Mrs. Nightingale

Billy Zane as Billy Zane

Jason Thorpe as Butler

Robert Cawsey as Waiter

Stanley Eldridge as Waiter

Oliver Maltman as Telegraph Operator

David Stoller as Hudson's Guard

Jack Riley as Newschild

Lilly Aspell as Newschild

Ethan Rouse as Newschild

Ellie Rose Eames as Newschild

Jamie Baughan as Titanic Ship Officer Liaison

Helen Duff as Titanic Guest

Jess Liaudin as Hangman

Wesley Kent-Hargreaves as Weird Child Companion

Daniel Fearn as Drooling Man Companion

Darren Lake as Disorientated Man Companion

Martin Bishop as Priest

Gerard Monaco as Titanic Ship Officer

Michael Buffer as Fight Fan #1

Bruce Buffer as Fight Fan #2

Russell Wilcox as Announcer

Hector Bateman-Harden as Young Sherlock Holmes

Codie-Lei Eastick as Young Watson

Laura Stevely as Sherlock's Mother

Layla Rose Boyce as Nicotine Stains / Nancy

Sadie Newman as Jane

Harry Baxendale as Seamus

Ella Bright as Bridgette

Kenneth Hadley as Headmaster

Paul Bigley as Teacher #1

Sue Maund as Teacher #2

Tommy Gene Surridge as Inky Hands

Paddy Holland as Tough Kid

Hugh Laurie as Mycroft Holmes (uncredited)

Steve Coogan as Gustav Klinger (uncredited)

Phil Hodges as Mr. Algernon Barkworth (uncredited)

Sara Beasley as Mrs. Frobisher (uncredited)

James Eeles as Manager Mr. Petrucka (uncredited)

Paul T.T. Easter as John (uncredited)

Jordan Long as Herbert (uncredited)

Sonnyboy Skelton as Doxy's Dad (uncredited)

Willem Dalby as Newsie Man (uncredited)

Riley White as Newsie Kid - Jimmy (uncredited)

Lochlan White as Newsie Kid - Timmy (uncredited)

John Kinory as Instructing Solicitor (uncredited)

Benjamin Lok as Courtroom Person 3 (uncredited)

Joseph Macnab as Fitness Instructor (uncredited)

Martin Bassindale as One Man Band (uncredited)

Amelia O'Loughlin as White Star-Line Girl (uncredited)

Matthew Di Liello as Telly-Phone Assistant (uncredited)

Craig Thomas Lambert as Yeoman of the Guard (uncredited)

Jorge Leon as British Soldier (uncredited)

Martyn Mayger as Buckingham Palace Guest (uncredited)

Hugh O'Brien as Garden Party Guest (uncredited)

Deepak Anand as Nobleman (uncredited)

Shawn Dixon as Upper Class Gentleman #1 (uncredited)

Anthony Richard Rowe as Victorian Gentleman (uncredited)

Mick Slaney as Docker (uncredited)

Karl Farrer as Russian Merchant (uncredited)