In October 2013, Walker represented Wales in the 2013 Rugby League World Cup. Walker made his international début against the United States in a match that also saw him score his first international try. Walker was back to playing in the Red Jersey of the Cymru in the 2015 European Cup tournament.[citation needed]
He scored a try in the opening game against Scotland.
Walker was born with a potentially fatal brain condition, arteriovenous malformation (AVM), however was not diagnosed until 2017, forcing him to retire days before the 2017 Rugby League World Cup.[7] Following treatment however, Walker was given the all-clear in April 2020 and was able to return to rugby.[8]