The teenage hooker, who has only started two league games for the club, is handed the honour by caretaker head coach Tommy McGee for the Championship trip to London Scottish.
Regular captain Ryan Burrows begins a three-game ban after being cited for trampling on Jonathan Thomas during the 36-17 loss against Worcester Warriors.
Flanker Jacob Rowan, who moved to Gloucester at the end of last season, was the previous youngest to wear the armband, taking on duties for Leeds Carnegie in 2012 when aged only 22.
Walker, then, is a comparative baby although he has had experience leading sides throughout his junior days including England Under-18s and Yorkshire Under-16s. His obvious talent was further highlighted when invited to train with England’s senior squad by Stuart Lancaster last year.
“It is a great opportunity but I don’t think much will change,” he said.
“It’s a name I’ve been given but we’ve 15 leaders in this team, not just one, and the lads will play just the same as ever.
“I do enjoy it. I like being a captain and, hopefully, I’ll lead from the front.
“The main thing is we go out there, play well and try get the result we need.”
Asked what McGee had said to him, Walker added: “Not much really. He just said to go and play my normal game as I’ve been given the captaincy for the way I’ve been playing and leading.
“As a team, we’ve been given a pretty simple game plan to follow, which hopefully should work and we’re looking forward to the test.”
Walker has missed just one of the last 11 games since coming in against Rotherham Titans in the B&I Cup in October and grown with confidence in each fixture.
Born in Settle and a product of the North Ribblesdale club, he has been playing alongside his elder brother Chris, the 22-year-old back-row, at Carnegie.
The club is boosted by the return of ex-England lock Chris Jones for the first time since October 5.
He is on the bench after recovering from injury while winger David Doherty is in the starting line-up after an eight-week absence as Yorkshire strive to improve on their eighth position.