Nix was raised in Canberra. Subsequent to a period working for the Australian Government, he traveled in Europe before returning to Australia in 1983 and undertaking a BA in professional writing between 1984 and 1986 at the University of Canberra. He worked in a Canberra bookshop after graduation, before moving to Sydney in 1987, where he worked his way up in the publishing field. He was a sales rep and publicist before becoming a Senior editor at HarperCollins. In 1993 he commenced further travel in Asia, the Middle East and Eastern Europe before becoming a full time marketing consultant, founding his own company Nix Evans Proprietary Ltd.

In addition to his work as a fantasy novelist, Nix has written a number of scenarios and articles for the role playing field, including those for Dungeons and Dragons and Traveller. These have appeared in related publications such as White Dwarf, Multiverse and Breakout!. He has also written case studies, articles and news items in the information technology field, his work appearing in publications such as Computerworld and PCWorld.

The Old Kingdom series

Also known as the 'Abhorsen Trilogy

• 1995 Sabriel
• 2001 Lirael
• 2003 Abhorsen
• 2010-2011 Clariel: The Lost Abhorsen Garth Nix's Amazon Blog: Clariel: The Lost Abhorsen and two other books Permalink
• 2011 (untitled)

Companion Books

• 2005 The Creature in the Case (especially produced for World Book Day) - Now also released as part of the collection below.
• 2005 (UK 2006) A Tale of the Abhorsen and Other Stories
• 2010 To Hold the Bridge (expected to be released in an anthology tentatively titled Australia’s Legends of Fantasy, edited by Jack Dann and Jonathan Strahan)

The Seventh Tower series

• 2000 The Fall
• 2000 Castle
• 2001 Aenir
• 2001 Above the Veil
• 2001 Into Battle
• 2001 The Violet Keystone

The Keys to the Kingdom series

• 2003 Mister Monday
• 2004 Grim Tuesday
• 2005 Drowned Wednesday
• 2006 Sir Thursday
• 2007 Lady Friday
• 2008 Superior Saturday
• 2010 Lord Sunday

Very Clever Baby series

These books were essentially self-published (though later republished by Text Media in Melbourne) and although aimed at "Very Clever Babies Aged 3-6 Months", some help is needed from parents with the long words such as "ichthyologist" used by the character Freddy the Fish.

• 1988 Very Clever Baby's First Reader
• 1988 Very Clever Baby's Ben Hur
• 1992 Very Clever Baby's Guide to the Greenhouse Effect
• 1998 Very Clever Baby's First Christmas

Other works

• 1990 The Ragwitch
• 1997 Shade's Children
• 2000 Serena and the Sea Serpent (in Aussie Bites series)
• 2005 "Read It in the Headlines!" in Daikaiju! Giant Monster Tales (ed. Robert Hood, Robin Pen)
• 2007 "Sir Hereward and Mister Fitz Go to War Again" in Jim Baen's Universe April 2007 (ed. Mike Resnick, Eric Flint)
• 2007 One Beastly Beast: Two Aliens, Three Inventors, Four Fantastic Tales — a book of short stories for younger readers, including Serena and the Sea Serpent
• 2009 A Confusion of Princes — a forthcoming young adult space opera novel [1]