Jonas's career started when he was discovered at the age of six in a barber shop, while his mother was getting her hair cut and was referred to a professional show business manager. At the age of 7, he began performing on Broadway. He had acted in several plays, including A Christmas Carol (in 2000 as Tiny Tim and Scrooge at eight), Annie Get Your Gun (in 2001 as Little Jake), Beauty and the Beast (in 2002 as Chip), and Les Misérables (in 2003 as Gavroche). After Les Misérables closed, he performed in The Sound of Music (as Kurt) at the Paper Mill Playhouse.
In 2002, while performing in Beauty and the Beast, Jonas wrote a song with his father called "Joy to the World (A Christmas Prayer)." With background vocals from the Beauty and the Beast cast, Nick recorded the song on the 2002 annual Broadway "Equity Fights AIDS" album, Broadway's Greatest Gifts: Carols for a Cure, Vol. 4. In November 2003, INO Records received a demo copy of "Joy to the World (A Christmas Prayer)". The label released the song to Christian radio, where it quickly became popular on Record & Radio's Christian Adult Contemporary Chart.
Jonas, along with his brothers, guest starred in an episode of Hannah Montana, which aired after the premiere of High School Musical 2 and the Disney Channel show Phineas and Ferb.
The reality short series, Jonas Brothers: Living the Dream, premiered on Disney Channel on May 16, 2008. The show, which ran until September 5, 2008, documents the brothers' lives on the Look Me in the Eyes Tour. The name was inspired by the band's hit song "When You Look Me in the Eyes". The series was renewed for a second season, which premiered on March 21, 2010. The second season follows the band on the European leg of their World Tour 2009. Jonas and his brothers filmed a Disney Channel Original Movie called Camp Rock where they play a band called "Connect Three." Joe plays the lead male role as lead singer "Shane Gray"; Nick plays the role of "Nate," a guitarist; and Kevin plays the role of "Jason," also a guitarist. A soundtrack for the movie was released on June 17, 2008. The movie premiered on June 20, 2008, in the USA on Disney Channel, and Canada on Family. Production began on the sequel, Camp Rock 2: The Final Jam in September 2009 and it premiered during the summer of 2010.
Jonas and his brothers starred in the Disney Channel Original Series JONAS about a pop band trying to live a normal life, which premiered May 2, 2009 and concluded on March 14, 2010. Filming for the second season began in February 2010. The second season was renamed Jonas L.A., and premiered on June 20, 2010. On November 8, 2010, it was announced that the series had been cancelled.
On June 21, 2010, Jonas made his West End debut performing in Les Misérables for the second time, but this time as the role of Marius Pontmercy. Jonas was originally supposed to play the role for only three weeks, but was able to extend his run until July 24, 2010, because of changes in the Jonas Brothers tour schedule. He also appeared in the 25th Anniversary Concert at The O2 Arena on October 3, 2010, again playing the role of Marius Pontmercy. From August 5–7, 2011, Jonas performed in the musical Hairspray as Link Larkin at the Hollywood Bowl. Jonas appeared in the 2011 series Mr. Sunshine; he played Eli White, an up-and-coming singer who wants everything his way before he performs at the Sunshine Center. He also plays the role of Ryan on the sitcom Last Man Standing.
By September 2004, an executive at Columbia Records discovered Jonas' song. He was soon jointly signed to INO Records and Columbia Records and released the single "Dear God". A second single, "Joy to the World (A Christmas Prayer)" (a re-recorded version), was released on November 16. It was supposed to be followed by a December release of a self-titled solo album Nicholas Jonas, but the album was pushed back. It did, however, get a limited release. Nick, along with his brothers, Kevin and Joe, co-wrote songs for the album. In early 2005, Columbia Records' new president, Steve Greenberg, heard Jonas' record. While Greenberg did not like the album, he did like Nick's voice.
Jonas' side project from the Jonas Brothers called Nick Jonas & the Administration released their debut album Who I Am was released February 2, 2010. In January 2010, Jonas embarked on the Who I Am Tour with the Administration. The tour consisted of 22 dates that began on January 2, 2010, in Dallas, Texas and concluded on January 30, 2010, in Berkeley, California. Jonas also toured with his brothers again in 2010. In September 2011 and October 2011, Nick Jonas & The Administration began touring through South America in support of their debut album, Who I Am.
Jonas was diagnosed with Type I diabetes at the age of thirteen and wears an OmniPod insulin pump to help him manage his condition. He has developed the Change for the Children Foundation. Partnering with five different charities, their goal is to raise money and awareness for diabetes. He also developed a public service announcement with the Washington Nationals to support diabetes care at Children's National Medical Center in Washington, D.C.
Since August 6, 2008, Bayer Diabetes Care has partnered with Jonas as a diabetes ambassador to promote the idea for young people to manage their diabetes. Jonas testified in the U.S. Senate to promote more research funding for the condition. In 2010, Nick further volunteered his efforts for Do Something by offering his time as a prize to teens who donated jeans to Do Something and Aeropostale's "Teens for Jeans" campaign. Further, Nick filmed another PSA, this one in support of Do Something's "Battle of the Bands" campaign, for the advancement of music education in schools. Nick is also is a member of the National Youth Leadership Committee for the Ronald Reagan Centennial Celebration, along with Jordin Sparks, Genevieve Ryan, and Brodi Conover.
Singer and actress Miley Cyrus has stated that she dated Jonas from June 2006 to December 2007. Cyrus claimed they were "in love" and began dating soon after they first met. Jonas dated Australian actress and singer Delta Goodrem from May 2011 to February 2012.