Fraser replaces the joint executive creative directors, Andy DiLallo and Jay Benjamin, who left in April 2007 to join Leo Burnett Sydney.
Fraser will work with Noel Magnus, the chief executive of JWT Australia & New Zealand, and report to Craig Davis, JWT's outgoing worldwide chief creative officer. His start date is not yet finalised, although he's expected to start imminently.
Fraser resigned from Rapier in March over a disagreement about its restructure, which would leave his role redundant.
Before Rapier, Fraser worked at DraftFCB and also spent 15 years as a creative partner at BMP DDB.
Fraser said: "JWT Sydney did very well at Cannes, which helped signal a creative resurgence for the agency. It will be my job to build on those successes."
Davis added: "Andrew's track record speaks for itself. His work goes well beyond television."