Walker began selling to Barneys New York in 1998, the same year she showed her first runway collection, and signed a partnership with the U.S. chain Anthropologie in late 2011. Her clothes have been worn by Björk, Sienna Miller, Natalie Portman, Rihanna and Jennifer Lopez, among many others, and by Kate Winslet in Eternal Sunshine of the Spotless Mind.
She was appointed a Member of the New Zealand Order of Merit in 2004 for services to fashion, and promoted to Companion in 2014. Beyond clothing, Walker is an expert on colour for interiors and has produced her own line of paint with Resene.