Newport-born Alex Walker has played for Newport Youth, Newport Gwent Dragons U20, and was part of the Dragons Junior Academy. He began his playing career aged 8, at mini rugby for Newport High School Old Boys. 

He gained his senior academy contract with the club at the start of the 2005–2006 season, making one replacement appearance for the region. Walker was an ever-present Dragons team member during the 2006–2007 season.

Walker has represented Wales at U18 and U19 levels. Walker was selected to play for the Wales U21 side in the 2005–2006 season but broke his collarbone, keeping him off the field for three months.

For the 2011/12 IRB World Sevens Series, he was named as one of Wales's 'core' contracted players. He was one of only two players - Richard Smith being the other - to feature in all nine tournaments throughout the campaign.