Australian-born Klonhammer is a former group account director at Wieden+Kennedy. For over a decade she has worked on brands such as Electronic Arts, Nike, Heineken, Microsoft and Carlsberg.
Klonhammer was instrumental in setting up the agency's digital offering and was responsible for securing their first digital client, Electronic Arts.
Since leaving W+K 18 months ago, she has had spells at Modernista! and 180. Prior to that, Klønhammer has spent time at Amirati Puris Lintas and TBWA\ Campaign in Sydney.
In her new role she will work closely with executive creative directors Colin Lamberton and Seyoan Vela to build the Dutch business and extend the strengthened Grey offering to international clients.
The creative pair, co-founders and creative directors of St. Lukes, joined Grey's EMEA team in London in 2007. They moved to Amsterdam in May 2008.
Klonhammer said: "It is the attitude of the people rather than particular categories or brands that is important to me. I like to work with people who are positive, highly motivated, fun loving and inspired by their work.
"I am a sucker for a good challenge. The Grey network has an exceptional reputation -- with Colin and Seyoan in the lead I feel confident we can make Grey Amsterdam a creative powerhouse. And have some fun along the way."
The newly established team will report directly to Carolyn Carter, Grey Group EMEA CEO.
"With Hazelle onboard, Grey Amsterdam's strategic-creative leadership balance is firmly established.
Carter said: "Clients, both current and future, local and international, will benefit from her significant digital background and prowess in managing integrated brand solutions without a creative bias associated with a particular market."
Grey Amsterdam's includes GSK, Procter & Gamble and Unilever Nederland.