McMahon was born in Concord, Massachusetts. He briefly lived in Ho-Ho-Kus, New Jersey until 1991, when his family moved to Bexley, Ohio where he attended Cassingham Elementary School. McMahon's family relocated frequently due to his father's occupation in retail. McMahon recalls that while he was in fourth grade, they briefly stayed in California to support his mother's family after the loss of her brother. Following the death of his uncle, who was an artist himself, McMahon became inspired to get involved with music and began teaching himself piano soon afterward.
McMahon's family decided to settle in California shortly before he entered eighth grade. He would later describe himself as "a pudgy, outgoing, artistic little kid who never quite fit into the California scene". He graduated from Dana Hills High School in 2000.
McMahon started playing the piano at age 9. The following year, he began performing piano solos before he could even read music. McMahon stated, "my mother was a good player and I started playing by ear. After a year of that, I began writing songs, and found outlets to perform them at school assemblies. Eventually, I got lessons."
McMahon started his first band, Left Here, with his high school friends and future Something Corporate bandmates Kevin "Clutch" Page on bass and Brian Ireland on drums in 1997. Even though they won a local battle of the bands competition, they soon broke up. McMahon went on to record the self-released eponymous four-track demo CD Andrew McMahon with the aid of several friends of his, including guitarist Josh Partington, whom he had met his sophomore year in high school. Joined by rhythm guitarist Reuben Hernandez (who was later replaced by William Tell), the quintet formed the piano rock band Something Corporate in 1998.
McMahon met the rest of the group in high school, and later decided on the moniker Something Corporate as a joke. Fronted by McMahon, the group recorded their self-released ten-song demo album Ready... Break in 2000, which led to a record deal with the indie record label Drive-Thru Records. Drive-Thru released the band's nationwide distributed debut EP Audioboxer the following year. McMahon's vocals, songwriting skills, and incorporation of the piano earned the album rave reviews and caught the attention of Drive-Thru's distributor MCA (now Geffen). Due to the labels' distribution deal, MCA was able to sign over Something Corporate and released their major label debut Leaving Through the Window in May 2002.
The band promoted the album by playing concerts across the United States, which included the main stage at Vans Warped Tour as well as supporting New Found Glory on their European tour. Something Corporate released their second full-length album North on Geffen Records in late 2003. As of 2004, the band is no longer under contract to any label.
On December 4, 2009, Something Corporate announced a reunion show at Bamboozle Left 2010 with an additional show later added at Bamboozle Chicago 2010. After Bamboozle, the band announced their reunion tour, which took place in August 2010.
The initial impulse behind McMahon's solo project Jack's Mannequin was "Locked Doors", a song he recorded in December 2003, which he felt was too different from previous Something Corporate material. He realized that, if he would ever decide to release it, it would be on a solo album rather than a Something Corporate record. The idea seemed to be off the table until, in late summer 2004, both McMahon and his bandmates were exhausted from months of touring and decided to take a break.
The first album Everything in Transit was released in August 2005. After the release and success of the first album, McMahon then proceeded to compose his second Jack's Mannequin album, The Glass Passenger, which was released in September 2008. Jack's Mannequin's third and final album, People and Things was released in October 2011. He stated that this new album "[would] probably have a bit of freeness" to it, distancing itself from The Glass Passenger.
On February 2, 2012, McMahon foreshadowed the end to Jack's Mannequin, saying, "I foresee an end to the usage of that name. I don't know that it's doing for me what it used to, in the sense that Jack's sort of really represented a freedom from something. And a really free approach to creating things that now is certainly wrapped up in a whole lot of turmoil and tumult in a very difficult time in my life. And to acknowledge that, I certainly think at some point I'm going to have to find a way to shake that loose. And I think to some extent that might mean retiring the name." On November 11 and November 12 of 2012, Jack's Mannequin performed their final shows under the moniker, coinciding with the annual Dear Jack Foundation benefit. In June 2013, Live From The El Rey Theatre was released to commemorate the final shows.
On August 25, 2012, the Jack's Mannequin website redirected to andrewmcmahon.com, with McMahon deciding to put out new music under his own name. Along with the promise of new music, it was announced soon after that he would be supporting the band Fun. on their tour in early 2013, with a solo headlining tour taking place in Spring 2013. McMahon played his first two solo shows in West Hollywood at the Viper Room in early January 2013.
On April 30, 2013, McMahon released The Pop Underground EP, produced by Mark Williams and Tony Hoffer, followed by an appearance on O.A.R.'s Sounds of Summer tour extending through August. Synesthesia became the first single launching McMahon's solo career, with an official music video that premiered on June 13, 2013.
In January 2013, McMahon was listed as one of the new songwriters for the second season of the NBC series Smash, signifying his first time writing for musical theatre. Showrunner Joshua Safran called McMahon the "wildcard of the bunch" of new songwriters hired for the second season, and was hired because Safran was a fan of his previous bands.
McMahon contributed three songs to the second season, I Heard Your Voice In a Dream, Reach for Me, and I'm Not Sorry. I Heard Your Voice In a Dream was met with critical acclaim, being nominated for an Emmy Award for Outstanding Music and Lyrics and has sold 10,000 digital downloads as of April 3, 2013.
On October 15, 2013, New York City venue 54 Below announced plans to stage Smash's fictional musical Hit List in concert format. On December 8 and 9, 2013, "Hit List" was performed for a three-show run, with McMahon in attendance. All three of his songs penned for Smash were performed, including his Jack's Mannequin track 'Swim' performed by Andy Mientus, on which McMahon played piano.
On July 11, 2014, McMahon posted on his website that the next progression in his musical career would be to tour and release music under the moniker of Andrew McMahon in the Wilderness. On July 16, 2014, he released his first single under the new project, entitled "Cecilia and the Satellite", named after his newborn daughter. During the summer of 2014, McMahon toured with Matt Nathanson and Gavin DeGraw in preparation for his first solo LP, Andrew McMahon in the Wilderness, released October 14, 2014, and coinciding with a full North American headlining tour. McMahon performed on the Weezer & Panic! at the Disco Summer Tour 2016 in support of Weezer and Panic! at the Disco On September 8, 2016, McMahon released a new single, "Fire Escape". On January 6, 2017, McMahon released a new single, "So Close".
His second solo album, Zombies on Broadway, was released on February 10, 2017.
On May 27, 2005 (three months before the release of Jack's Mannequin's debut album Everything in Transit), McMahon was forced to cancel all of his upcoming concerts. After a medical examination in connection with a relentless case of laryngitis, McMahon was admitted to a hospital in New York City, where he was diagnosed with acute lymphoblastic leukemia on June 1, 2005, the same day he finished recording Everything in Transit. Since the illness was diagnosed in its early stages, McMahon's doctors had high hopes for a full recovery.
Over the following couple of months, McMahon received various types of treatment, all the while updating his blog to keep his fans informed on the progress of his condition. August 23, 2005 marked a very significant date for him for two reasons: it was the day his album Everything in Transit was released, debuting at #37 on the Billboard 200 with over 22,000 copies scanned within its first week, as well as the day he received a stem cell transplant, with his sister Katie McMahon serving as the donor.
On December 2, 2005, McMahon celebrated the 100-day anniversary of his stem cell transplant by playing his first concert in six months: a private invite-only show in a small venue in Los Angeles, California. His first public appearance followed ten days later at "Gimme Shelter '05", an acoustic cancer benefit concert at the Roxy in Los Angeles, California. Following these shows, Maverick Records finally started a promotion campaign for Everything in Transit, including TV appearances by McMahon on Jimmy Kimmel Live!, One Tree Hill (in the episode "Just Watch the Fireworks"), Last Call with Carson Daly, Steven's Untitled Rock Show, and The Late Late Show with Craig Ferguson, as well as a second music video for "The Mixed Tape", which hit #1 on VH1's VSpot Top 20 Countdown on June 9, 2006.
In July 2006, McMahon founded a non-profit charity, entitled The Dear Jack Foundation, to raise funds for cancer research. The organization's primary beneficiaries are the Pediatric Cancer Research Foundation, the Leukemia and Lymphoma Society and the regents of the University of California, Los Angeles.
A documentary entitled "Dear Jack" was released on October 8, 2009 on DVD by Warner Bros, and was shown at theatrical screenings in New York, Chicago, and Los Angeles. The film, which chronicles McMahon's struggle with leukemia, features self-recorded footage in the hospital and is narrated by his friend Tommy Lee. The documentary was directed by Corey Moss and Josh Morrisroe, two former MTV News producers who covered McMahon's story for the channel, although much of the intensely personal footage was shot by McMahon himself.
McMahon married his longtime girlfriend, Kelly, in December 2006. In September 2013 he revealed that they were expecting their first child. Their daughter, Cecilia Kate McMahon, was born February 13, 2014.
In 2014 after the announcement of their second annual Light the Night walk, The Dear Jack Foundation announced that over eight years they raised a half a million dollars for The Leukemia & Lymphoma Society.For McMahon's releases with Something Corporate, see Something Corporate's discography
For McMahon's releases with Jack's Mannequin, see Jack's Mannequin's discography