Regular captain Brett D'Oliveira has been drafted into The Hundred by Birmingham Phoenix
Jake Libby will captain Worcestershire for the remainder of the Royal London Cup.
The 29-year-old, who is Worcestershire's vice-captain in red-ball cricket, takes over from Brett D'Oliveira after he was drafted into The Hundred by Birmingham Phoenix as a replacement for Tom Abell.
Libby has made eight List A appearances for Worcestershire, scoring 239 runs.
Assistant coach Alan Richardson said: "Jake will now be captain. He has shown some real interest in leadership roles within the squad, and he is an experienced and very skilful player.
Regular captain Brett D'Oliveira has been drafted by Birmingham Phoenix for The Hundred [Michael Steele/Getty Images]
"I'm pleased for Brett that he has got that opportunity with the Phoenix. It is something he has worked hard to get recognition for; he has been really driven and pushed himself.
"That is great for Brett and it gives Jake an opportunity to experience some more leadership and captain the side throughout the competition.
"He has had some experience of it before and stepped in at times for us since he's been vice-captain and done a really good job. It will be a good experience for him leading the group through these stages."