Noonan grew up with a strong background in classical music, with her mother Maggie being a well-known opera singer. She studied opera and jazz at the Queensland Conservatorium.
After graduation, Noonan began fronting the pop-rock group george, along with her brother Tyrone Noonan. Noonan founded george with her brother, with whom she shares lead vocals, in 1996 to enter a university music competition. After a series of successful independently released EPs, they signed to Festival Mushroom Records and released the debut album Polyserena in 2002, which debuted in the number 1 position on the Australian Recording Industry Association (ARIA) albums chart. george won the Breakthrough Artist ARIA award in 2002 and performed the song "Breathe in Now" at the award ceremony.
Noonan founded the jazz trio Elixir in 1997, which released their debut self-titled album in 2003. Elixir's second album First Seed Ripening was released on 5 August 2011. It won the 2011 ARIA Award for Best Jazz Album.
Noonan released an album of jazz and operatic duets with her mother in 2004. Entitled Two of a Kind, the album was released by the ABC Classics label.
In 2004, Katie guest appeared at the Lord Of The Rings Symphony. Reviewer Murray Black said; "The undoubted highlight of the evening was guest vocalist Katie Noonan. Here is a rare talent with a voice of extraordinary beauty and versatility. In most of her solos, she sounded like a classical soprano as she soared over the orchestra with a spine-tingling, vibrato-less angelic purity. Then, in Gollum’s Song and the Oscar-winning Into the West, she revealed her pop diva credentials with her strong, clear voice projecting effortlessly out in the audience."
Paul Grabowsky and Noonan teamed up for the jazz cycle Before Time Could Change Us. Consisting of words written by Dorothy Porter, the album tracks "the mysterious shifts and changes of a relationship." The album won the 2005 ARIA Award for Best Jazz Album.
Later in 2005, Noonan was invited by Deborah Conway to take part in the Broad Festival project—together with three other Australian female artists they performed their own and each other's songs. Sara Storer, Ruby Hunter and Clare Bowditch were the other female artists.
Noonan recorded a solo album entitled Skin at Sydney's Linear Recording in 2006. Produced by Andrew Klippel, Skin was released on 11 August 2007, and debuted at number 6 on the ARIA 'Top 50' album charts and number 1 on the Australian ARIA 'Top 20' album chart. The debut single "Time To Begin" debuted at number 30 on the ARIA Top 50.
Following the success of the remix of "Time To Begin", Noonan collaborated with John Course and Mr Timothy. The collaboration involved the re-recording of Noonan's vocal tracks and a dance version of her solo album was released under the title Second Skin.
On 22 February 2008, Noonan was a support act for Cyndi Lauper at King's Park Botanic Gardens, Perth, Western Australia, and was invited on stage by Lauper to sing along to "Girls Just Want to Have Fun". Also in 2008, Noonan was featured as the vocalist in Telstra's "I Am Australian" series of advertisements.
Noonan released a jazz album of Lennon and McCartney cover versions in 2008 entitled Blackbird: The Music of Lennon and McCartney.
The Katie Noonan and the Captains album Emperor's Box was created over a three-year period and is Noonan's second release for Sony Music. Noonan wrote all of the songs and collaborated with the following artists during the recording of the album: Tim Finn (Split Enz), Sia Furler, Don Walker (Cold Chisel), Josh Pyke and Australian writer/poet Tom Shapcott. The album was co-produced by Noonan and Nick DiDia (Pearl Jam, Bruce Springsteen, Stone Temple Pilots, Powderfinger). It was preceded by the single "Page One" released in February.
In 2011, Noonan collaborated with Karin Schaupp and toured Songs from the British Isles. An ep was released available only from Noonan's website. In 2012, the two recorded Songs of the Southern Skies. The album was nominated for two ARIA Awards at the 2012 ceremony.
In 2013, Noonan released Songbook, an album that saw Noonan re-recording songs from her time in george and Elixir. She also worked with the Sydney Dance Company on the production; Les Illuminations.
In 2014, she released Fierce Hearts which was nominated for an ARIA Award at the 2014 ceremony. it was music alongside a contemporary circus show by Circa.
In 2015, Noonan released Transmutant through Universal Music Australia. The album peaked at number 33 on the ARIA Charts.
In 2016, Noonan collaborated with Brodsky Quartet and released With Love and Fury in April. They toured Australia throughout April and May.
In December 2016, Noonan announced the release Songs of the Latin Skies with Karin Schaupp. The album due for release in February 2017 and will see the duo embark on a musical journey through the South American songbook, exploring the sounds and beats of the bossa nova, salsa, tango and samba. The duo will play live shows across the country from the middle of March.
A National Office for Live Music was launched by Australian Prime Minister Kevin Rudd in July 2013 and, as of August 2013, Noonan is the state ambassador for Queensland.
In 2013, Noonan combined with the Sydney Dance Company and musicians from the Sydney Symphony Orchestra and conductor Richard Gill to perform Britten's song cycle Les Illuminations at Sydney's City Recital Hall Angel Place. This production was taken in 2014 to Brisbane's QPAC with the Queensland Symphony Orchestra under Johannes Fritzsch.
Noonan will be the official ambassador to the Adelaide Fringe Festival in 2014.
Noonan is married to Isaac Hurren, her longtime partner and collaborator in Elixir. They are parents to two sons.