| Movie | 2001 | The Lord of the Rings: The Fellowship of the Ring | Merry | |
| Movie | 2002 | The Lord of the Rings: The Two Towers | Merry | |
| Movie | 2003 | The Lord of the Rings: The Return of the King | Merry | |
| Movie | 2009 | X-Men Origins: Wolverine | Bradley | |
| Movie | 2008 | I Sell the Dead | Arthur Blake | |
| Movie | 2004 | Spivs | Goat | |
| Movie | 2005 | The Purifiers | Sol | |
| Movie | 2005 | Ringers: Lord of the Fans | Self - Narrator | |
| Movie | 2005 | Shooting Livien | Owen Scott | |
| Movie | 2011 | The Day | Rick | |
| Movie | 2012 | The Millionaire Tour | Casper | |
| Movie | 2012 | Soldiers of Fortune | Sin | |
| Movie | 2003 | Film Collectibles: Capturing Movie Memories | Self | |
| Movie | 2000 | This Is Personal: The Hunt for the Yorkshire Ripper | | |
| Movie | 2016 | Pet | Seth | |
| Movie | 2015 | Molly Moon and the Incredible Book of Hypnotism | Nockman | |
| Movie | 2003 | An Insomniac's Nightmare | | |
| Movie | 2004 | A Filmmaker's Journey: Making 'The Return of the King' | Self | |
| Movie | 2017 | Atomica | Robinson | |
| Movie | 2001 | Quest for the Ring | Self | |
| Movie | 1997 | Hostile Waters | Sasha | |
| Movie | 2001 | A Passage to Middle-Earth: Making of 'Lord of the Rings' | Self | |
| Movie | 2012 | Detention | Lead Singer of The Drunges | |
| Movie | 2018 | Mute | Oswald | |
| Movie | 2017 | A Midsummer's Nightmare | Mike Puck | |
| Movie | 2004 | Frodo Is Great... Who Is That?!! | Self | |
| Movie | 2019 | Star Wars: The Rise of Skywalker | Beaumont Kin | |
| Movie | 2001 | Beyond the Movie: The Fellowship of the Ring | Self | |
| Movie | 2019 | Radioflash | Chris | |
| Movie | 2009 | Wolverine Unleashed: The Complete Origins | Self | |
| Movie | 2020 | The Skywalker Legacy | Self | |
| Movie | 2018 | Waterlily Jaguar | Bill | |
| Movie | 2022 | Last Looks | Warren Gomes | |
| Movie | 2021 | Edge of the World | Crookshank | |
| Movie | 2002 | The Making of The Fellowship of the Ring | Self | |
| Movie | 2003 | The Quest Fulfilled: A Director's Vision | Self | |
| Movie | 2024 | The Lord of the Rings: The War of the Rohirrim | Wrot (voice) | |
| Movie | 2025 | Long Shadows | Ned Duxbury | |
| Movie | 2003 | The Making of The Two Towers | | |
| Movie | 2004 | The Making of the Return of the King | Self | |
| TV Show | 2011 | Goodnight Burbank | Paul Lynch | 6 |
| TV Show | 2004 | I Love the '90s | Self | 10 |
| TV Show | 2003 | The Ellen DeGeneres Show | Self | 2 |
| TV Show | 2003 | Jimmy Kimmel Live! | Self | 4 |
| TV Show | 1997 | The View | Self | 1 |
| TV Show | 1988 | LIVE with Kelly and Mark | Self - Guest | 1 |
| TV Show | 2006 | Rachael Ray | | 1 |
| TV Show | 1992 | The Tonight Show with Jay Leno | | 3 |
| TV Show | 1995 | MADtv | Self | 1 |
| TV Show | 2004 | Lost | Charlie Pace | 74 |
| TV Show | 1993 | Late Night with Conan O'Brien | Self - Guest | 1 |
| TV Show | 2010 | Top Gear | | 1 |
| TV Show | 1996 | Hetty Wainthropp Investigates | Geoffrey Shawcross | 27 |
| TV Show | 2009 | FlashForward | Simon Campos | 22 |
| TV Show | 2015 | The Late Show with Stephen Colbert | Self | 1 |
| TV Show | 2022 | Moonhaven | Paul Sarno | 6 |
| TV Show | 2008 | Childrens Hospital | Oren Maestro | 1 |
| TV Show | 2000 | Monsignor Renard | Etienne Pierre Rollinger | 4 |
| TV Show | 2007 | Chuck | Tyler Martin | 1 |
| TV Show | 2015 | 100 Code | Tommy Conley | 12 |
| TV Show | 2012 | The Unknown | Mark Nickel | 6 |
| TV Show | 2024 | Angry Birds Mystery Island | Hamylton (voice) | 24 |
| TV Show | 2013 | Wild Things with Dominic Monaghan | self | 31 |
| TV Show | 2017 | Talking with Chris Hardwick | Self | 1 |
| TV Show | 2003 | Punk'd | Self | 1 |
| TV Show | 2005 | The Late Late Show with Craig Ferguson | Self | 1 |
| TV Show | 2012 | The Eric Andre Show | Self | 1 |
| TV Show | 2022 | The Legend of Vox Machina | Archibald Desnay (voice) | 3 |
| TV Show | 2015 | The Late Late Show with James Corden | Self - Guest | 1 |
| TV Show | 2011 | Ridiculousness | Self | 1 |
| TV Show | 2013 | @midnight with Chris Hardwick | Self | 1 |
| TV Show | 2016 | Quantum Break | William Joyce | 4 |
| TV Show | 2018 | Bite Club | Stephen Langley | 8 |
| TV Show | 2009 | Watch What Happens Live with Andy Cohen | Self - Guest | 1 |
| TV Show | 2013 | Hollywood Game Night | Self | 1 |
| TV Show | 2011 | Death in Paradise | Bank Manager | 1 |
| TV Show | 2020 | Reunited Apart | Self | 1 |
| TV Show | 2025 | Billy & Dom Eat the World | Himself | 8 |
