Cilmi was born in the Melbourne suburb of Dandenong. Of Italian descent, she lives with her parents Paula and Joe (whose origins are in Calabria) and

Cilmi was born in the Melbourne suburb of Dandenong. Of Italian descent, she lives with her parents Paula and Joe (whose origins are in Calabria) and her brother Joseph.
At an early age Cilmi developed an interest in a wide range of musical styles including Nina Simone, Led Zeppelin, Janis Joplin, The Sweet, T.Rex and Cat Stevens. Despite her natural aptitude and vocal talent, she was told that she lacked the discipline necessary to pursue a singing career. Idolising Janis Joplin, during this time she sang with a band performing cover songs by Led Zeppelin, Jet, Silverchair and others. Cilmi recorded original songs with writer/producers Barbara and Adrian Hannan of The SongStore.SongStore biography
In 2004 Cilmi captured the attention of Warner Music executive Michael Parisi whilst giving an impromptu rendition of the Rolling Stones' song "Jumping Jack Flash" at the Lygon Street Festa, a community festival in Melbourne. At the age of thirteen Cilmi travelled to the US and UK with Adrian Hannan and was offered four major US deals. She eventually signed a contract with Island Records UK.

The tracks "Don't Tell Me" and "Sorry", co-written with Barbara and Adrian Hannan, appeared on the soundtrack of 2005 Australian film Hating Alison Ashley.
Cilmi shares a manager (Cassandra Gracey), writer/producers (Xenomania) and UK record label (Island) with the Sugababes, and supported former Sugababe Mutya Buena at the Jazz Café in London in 2007. She made her UK TV debut on 14 December 2007 when she sang her new single "Sweet About Me" on Later with Jools Holland. In December 2007 Cilmi's song "Sanctuary" featured in the film St Trinian's and on .
Cilmi has also sung on the theme to UK TV Series Echo Beach which aired in early 2008 on ITV1. It is a cover of "Echo Beach" by Martha and the Muffins.

In February 2008 she supported the Parisian band Nouvelle Vague on their UK tour.
Cilmi's first album Lessons To Be Learned was written and recorded with hit production team Xenomania and was released on 31 March 2008 in the UK. She has been compared to Amy Winehouse, Anastacia and also Macy Gray, because of the occasional fracture in her voice.