Giles was linked with the county when they advertised for a director of cricket last year but will instead take on the top job from July 3. The position has been vacant since 2019, with chair Fanos Hira taking an active role in the running of the club.
Giles spent his entire playing career with Warwickshire, Worcestershire's local rivals, and also had two stints as director of cricket at Edgbaston - but has emphasised his desire to "make a meaningful contribution" to his new club.
"Having resided in Worcestershire for 25 years, having married and raised my children here, I have developed a deep appreciation for the club's rich history and recognise the immense potential for an exciting and promising future," Giles said.
"I am eager to make a meaningful contribution to the club's growth and success and am looking forward to the opportunity to connect with our passionate members and supporters, and collaborate with the entire club community to ensure exceptional performance both on and off the field."
Hira said that the club's board - who approved Giles' appointment unanimously - were "delighted" to announce his arrival. "His unparalleled expertise and exceptional track record in cricket administration make him the definitive choice to lead our organisation into a transformative era," Hira said.
"We possess utmost confidence that his dynamic leadership and unwavering passion for the sport will serve as indispensable assets in propelling us towards success on and off the field."
A club statement said that Giles would provide support to Worcestershire's coaching teams as well as overseeing the management of the club more widely.