In January 2006, Plunkett was appointed Australian Ambassador to Ireland, with concurrent accreditation to the Holy See. Her Holy See appointment was formalised by Pope Benedict XVI on 18 May 2006 when he accepted her letters of credence. While Ambassador to the Holy See, Plunkett accepted a Papal rebuke over Australia's treatment of its Aboriginal people, when the Pope called for ongoing attention to the social situation of Aboriginal people. As ambassador in Ireland, during her frequent public appearances, Plunkett was noted for her ability to "pepper" ambassadorial speeches with "amusing anecdotes."