Ms Willmott will take up the role in the first quarter of next year.
She has recently been working as director of external relations for Fortescue Metals Group, a role she took on in 2010.
It is believed she has chosen to move to a new role after helping FMG complete all approvals for its planned production expansion to 155 million tonnes per year.
Cannings Purple managing director Warrick Hazeldine said the company was thrilled to have attracted Ms Willmott to its board.
“Deidre’s unique skill set is a perfect fit with Cannings Purple’s core business offerings, which are highly geared to the resources, energy and related professional services sectors,” Mr Hazeldine said in a statement.
“In particular, Deidre brings extensive knowledge of both state and federal government, including strong experience in project approvals, which will be of tremendous value to our resources and energy sector clients.”
Mr Hazeldine said Ms Willmott would work closely with director of government relations Richard Harris at Cannings Purple.