Muncey was born in Melbourne, and attended St Bedes College (high school) with future bandmates Nic and Chris Cester. Muncey took up guitar after hearing "Sunshine Of Your Love" by Cream. The song "Timothy" from "Get Born" was written about an older brother named Timothy who died in infancy before Muncey was born. Muncey and Nic Cester became best friends at school, with Cester declaring "He had 'Led Zeppelin' written on his bag, and so did I, so it was inevitable, I guess", on the band's documentary recorded on their DVD, Right! Right! Right!.
In addition to playing lead guitar, Muncey sings lead vocals on a number of Jet's songs, including "Hey Kids", "Radio Song" and more recently "She Holds A Grudge".
Muncey married his girlfriend Sarah Rumbelow, on 18 August 2009.