Osment's entry into the entertainment industry began in 1998, when she was cast in a commercial for flower delivery company FTD. From there she went on to feature in many commercials, after which she made her acting debut in the 1999 film The Secret Life of Girls, starring Eugene Levy and Linda Hamilton. The same year, she co-starred with Glenn Close in the Hallmark Classic telefilm Sarah, Plain and Tall: Winter's End, a role that would lead a Young Artist Award nomination. Since then, she has gone on to do a number of roles, such as appearances on television shows like Touched by an Angel, Friends, and 3rd Rock from the Sun.
In 2003, Osment made her film debut as Gerti Giggles in Spy Kids 2: Island of Lost Dreams which grossed $229 million globally and for which she won the "Young Artist Award" for best performance in a feature film. In 2003, she reprised her role in the third part of the Spy Kids series, Spy Kids 3-D: Game Over, which grossed $197 million worldwide.
In 2006, Osment got the role of Lilly Truscott in the Disney Channel series Hannah Montana. The series premiere scored record ratings for the Disney Channel with 5.4 million viewers, a response "beyond our wildest expectations", according to the president of Disney Channel Entertainment.
The show earned her a Young Artist Award nomination in 2007 for best performance in a TV series (Comedy or Drama). She also appeared in the Disney Channel Hannah Montana promotion "Hannah Montana's Backstage Secrets", in which she portrays Lola in a fictional interview set in the show's canon. In addition, she helped to design some of the pieces from the Hannah Montana clothing collection which Disney released in the latter part of the summer in 2006. On December 25, Osment hosted the Walt Disney World Christmas Day Parade with Hannah Montana co-star Mitchel Musso. The parade featured acts like Miley Cyrus and the High School Musical cast. She and Musso performed a sketch based on a Hannah Montana episode. She also had a voice over role in a movie called Holidaze: The Christmas That Almost Didn't Happen, which also featured the voices of fellow Disney Channel stars Brenda Song and Dylan and Cole Sprouse. She performed several songs for the movie, including "Don't Ya Just Love Christmas" and "One Day".
Osment did a voice-over role in the Disney movie Lilo & Stitch 2: Stitch Has a Glitch and also a voice role in Edward Fubbwupper Fibbed Big. She also starred as a goth in R. L. Stine's: The Haunting Hour: Don't Think About It (co-starring with Hannah Montana co-star Cody Linley). It earned her a Young Artist Award nomination in 2008 for "Best Performance in a TV Movie, Miniseries or Special Leading Young Actress". In 2007, she guest starred as Kelly and tall skunk girl on Disney Channel's Shorty McShorts' Shorts.
In May 2011, she released her next single "Hush" to Canadian Radio. The song is a duet between her and Josh Ramsay of Marianas Trench. Osment finished filming Cyberbully an ABC Family TV film in Montreal starring Kelly Rowan and Kay Panabaker. Osment was the role of "Taylor Hillridge" a victim of cyber bullying. It premiered July 17, 2011. In 2012, Osment announced (via Twitter) that she will be guest starring in an episode of Life With Boys and four episodes of Family Guy. She also will portray Shelby in the 2013 drama film "Kiss Me", a film about a girl with scoliosis. She reprised her voice role as Pep for the third Beverly Hills Chihuahua film, which was released on DVD September 18, 2012.
Osment also recorded a remake version of the song "If I Didn't Have You" with Mitchel Musso for the DisneyMania 6 CD. The song was produced by Bryan Todd. The two also filmed a music video for their remake. In addition, she also recorded a song, released in 2008, with "The Disney Channel Circle of Stars". She recorded a remake of "Once Upon a Dream" for the release of Sleeping Beauty 50th Platinum Edition. The song was aired on Disney Channel on September 12, 2008. She also recorded a song called "Hero in Me" for the Disney Channel Original Movie, Dadnapped. She also filmed a music video to accompany it. The song will also be released on the Disney compilation album Disney Channel Playlist, which was released June 9, 2009. According to an audio interview with Osment backstage at the Grammys, she is to start filming a new movie called Soccer Mom. In April 2008, Parade magazine and Forbes ranked her #1 in their Hot Kid Stars To Watch list. She also starred in the Disney Channel Original Movie, Dadnapped. The film premiered in February 2009.
According to an audio interview with Osment backstage at the Grammys 2008, she is currently writing and recording tracks with Eve 6. In an interview with Half Taft Blue in 2008, she said that she is working on her EP which is called All the Right Wrongs, though the sound will be completely different from Disney pop. Instead, the main genre will be Indie rock, and the EP will be released. She is set to write most of the songs on the album, with the new track "All The Way Up" being premiered on Radio Disney in August 2009. Osment describes her music as "definitely Pop but with an Alternative rock edge." She has collaborated on tunes with Tom Higgenson, Max Collins, Tony Fagenson, Toby Gad and Mandi Perkins. On September 18, 2009, Osment tweeted the songs that would be featured in her EP on her official Twitter page.
On March 24, Osment confirmed on Good Day NY that her debut album is set to be released in the Summer 2010. The first single, "Let's Be Friends" from her debut album premiered on JSYK.com on June 7, 2010. On June 3, it was announced that the album would be released in the fall. She announced via Facebook on August 16 that her album would be released in the US on October 5 and that it would be titled Fight or Flight. The cover art was revealed August 17. The next single off Fight or Flight was "Lovesick".
To the film, she released her newest single "Drift". Which is also featured in Cyberbully. In 2012 Osment confirmed on her official Facebook account, that she had left Wind-Up Records and is pursuing a "folk" sound for her next album. She started a new music project with her new college friend Daniel Schechter, a indie folk duo called Ramshackle.
Emily is currently dating Sterling Knight.