The teenage hooker, who has only started two league games for them, is handed the honour by caretaker head coach Tommy McGee for the Championship trip to London Scottish.
Regular skipper 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 gameplan 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.
“It is cool,” said Walker, whose mother Suzanne represented Zimbabwe as a swimmer and late father Johnny was a winger for Otley, Hunslet, Batley and Keighley Cougars.
“It’s something I always wanted to do and to now be doing that is a massive pleasure.
“It’s going great at the moment. It’s awesome to be playing so much, I’m enjoying the rugby and obviously the opportunities I’m getting.
“Losing Ryan is a loss as he’s been playing well all season but I’m sure the lads coming in will step up and help us get the win.”
Carnegie are currently eighth in the Championship, their loss against leaders Worcester their first defeat in six games. They hope to quickly bounce back against a Scottish side who have dropped to fourth following consecutive defeats to Worcester and Nottingham and have lost four games running in all competitions.
Carnegie trail them by 13 points and Walker admitted: “It would be great to go get the result down there to try and climb back up the table as we are still aiming for the top four.
“It is a big game but not one we’re seeing as must-win.
“They are a tough team as they have proved so far this season given they are fourth in the league. I don’t think the last two defeats in the Championship make much difference to that.”
It will only be Walker’s 18th senior appearance for the club which again demonstrates the faith McGee has in him.
Carnegie are 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 back in the starting line-up after an eight-week absence.