A native of New Jersey, Canonico has been performing since he was six years old. He was first interested in modeling, but after the first audition he decided that modeling was too boring for his taste. His mother suggested acting instead. He has been a musician since he was 10 years old, starting with voice and moving on to drums and guitar. Both his parents are musicians and his father is a music teacher. A resident of Matawan, Canonico attended Mater Dei High School.
His first Broadway performance was in 1999, playing Gavroche in the musical Les Misérables. He played the role for a year and a half before leaving to do A Christmas Carol at Madison Square Garden in 2001, playing the role of Jonathan.
While he was still performing in Les Misérables he became involved in readings for the off-Broadway musical The Prince and the Pauper at the Lamb's Theatre. He played the Pauper Tom Canty from the show's opening on June 16, 2002 until October, when the show took a month-long break. The show opened again in November without Canonico, who had grown out of the role (and was replaced by Jimmy Dieffenbach). In 2004 Canonico played Brett in the off-Broadway musical Children's Letters to God, also at the Lamb's Theatre.
Canonico performed as an ensemble member and as an understudy for all male roles (excluding Melchior Gabor) in the Broadway musical Spring Awakening, which opened on November 10, 2006, at the Eugene O'Neill Theatre. He took over the role of Moritz from August 4, 2008, until the show closed on January 18, 2009.
In the summer of 2009 Gerard was involved in American Idiot, a musical based on the hit Green Day album, along with fellow Spring Awakening cast members Brian Charles Johnson and John Gallagher, Jr.. American Idiot premiered in Berkeley, California on September 4, 2009. Gerard stayed with the show until its April 24, 2011 closing as a member of the ensemble while also understudying two other featured ensemble tracks.
Canonico appeared as Goliath in the Off-Broadway production of "Stand Tall", a musical based on the story of David and Goliath. This was presented as part of the NYMF Festival during the summer of 2012.
He appeared as the principal role of Matt in the rock musical Bare at the New World Stages in NY. This is a story about a group of teens as they wrestle with their identities, sexuality, and religion at a co-ed Catholic boarding school and navigating the complex road from adolescence to adulthood. His character has the problem of always being second best to the school's golden-boy, Jason. His girlfriend, Ivy, breaks up with him for Jason. Previews began on November 19, 2012 and the show officially opened on December 9, 2012. It ran through February 3, 2013.
Canonico performed the role of Rich Goranski in the original cast of the world premiere of the musical Be More Chill. The show performed at the Two River Theater from May 30th to June 28th, 2015 at the Two River Theater in Red Bank, New Jersey.
Canonico appeared in the World Premiere of the Off Broadway show "Brooklynite" (reuniting with Spring Awakening director Michael Mayer as well as former castmates Matt Doyle and Remy Zaken) at the Vineyard Theatre. The show ran from January 30 - March 22, 2015.
Canonico will return to Broadway in the Tim Minchin musical adaptation of "Groundhog Day", based on the Bill Murray film. Previews began March 16, 2017 at the August Wilson Theatre, with the official opening on April 17, 2017.
Canonico has been a member of the band Taking Chances, as lead singer and playing guitar,in which he wrote the music and lyrics, since Christmas 2006, along with the Salerno brothers, Nick, Chris, and Joe. They are an alternative rock band from Hazlet, New Jersey. The music ranges from upbeat pop to rock, and with ska, reggae, and light acoustic songs. Their influences include Green Day, Jimmy Eat World, the All American Rejects, Foo Fighters, and David Bowie They released a CD in April 2008, self-titled "Taking Chances".
He is currently playing drums with Declan Bennett at various clubs around NYC and can also be heard on the CD "Record:Breakup".
- 2015 "Be More Chill" cast album
- 2014 21 Chump Street cast album
- 2012 "Record: Breakup"
- 2010 "American Idiot" cast album
- 2008 "Taking Chances" 
- 2007 "Spring Awakening" cast album
- 2004 "Children's Letters to God" 
- 2002 "The Prince and the Pauper"
- Hemhauser, Danielle. "Setting the stage", Asbury Park Press, March 28, 2006. Accessed August 10, 2012. "Mater Dei High School is connected to Broadway through Gerard Canonico, 16, a junior from Matawan."
- Broadway role in A Christmas Carol
- Regional theatre
- The King and I
- The Prince and the Pauper off-Broadway
- Canonico fansite
- Spring Awakening
- Taking Chances
- Taking Chances