[2] Walker joined the New Zealand junior team in 2019, throwing lead rocks for the country, on a rink skipped by Matthew Neilson.

[4] At the 2020 World Junior Curling Championships, the team finished with a 3–6 record, in 8th place,[5][6] relegating their country to the B event, which was cancelled due to the COVID-19 pandemic.

There, he led the New Zealand team of Jayden Bishop, Sam Flanagan and William Becker to a 4–2 record, just missing the playoffs, and finishing 11th overall.

[7] As a junior, Walker also competed at the 2020 Winter Youth Olympics, where he skipped the New Zealand team, which also consisted of Zoe Harman, Becker and Lucy Neilson.

Walker led the team to a 4–1 finish in group play, then defeated Germany in the quarterfinals, before losing to Japan in the semifinals.