Born in Upper Hutt, he received a bachelor's degree in English Literature from the University of Otago and a master's degree in English Literature from the University of Auckland. In 1995 he represented New Zealand at the University of Iowa's International Writing Program.

Johnston edited the books page of (the now-defunct) The Evening Post from 1991-1996. In 1997 he moved to London and started working as a "casual sub-editor on the broadsheets", but after eight months moved to Normandy to teach English. When the job fell through, he commuted once a week across the Channel to work part-time for The Observer newspaper.

His marriage in 1998 resulted in his getting the right to work in France, and he applied for and received a job as an editor at the International Herald-Tribune in Paris. He moved there in 1999 with his wife, Christine. They have a son, Emile.

Johnston also edits "The Page", a Web site that features poems and essays from elsewhere on the Internet. "I'd always wanted to find a web site that kept track of the best new writing about poetry, and couldn't find it, so I made it myself," Johnston said in a 2007 interview. "It's a lot of fun, though I find it hard attending to it regularly."

In 2007 he became the J.D. Stout Fellow at Victoria University. He is living in New Zealand for a year, writing a book about contemporary New Zealand poetry.

Poetry:

• 2007: Sol, Victoria University Press
• 2000: Birds of Europe, Victoria University Press
• 1999: The Open Window, Arc Publications (United Kingdom)
• 1996: The Sounds, Victoria University Press
• 1993: How to Talk, winer of the 1994 New Zealand Book Award for Poetry and the 1994 Jessie Mackay Best First Book Award, Victoria University Press