She joins senior partner Fraser Hardie, partner Chris Jones and MD Gordon Tempest-Hay on the 40-strong agency's board.
Joyce continued to work with PN, which she joined in 1988, as lead consultant on its NHS work until last week.
At Blue Rubicon she will advise clients including McDonald's, Unilever and GlaxoSmithKline. She will also focus on new business and ‘people development' for the agency's 40 staff.
Joyce has been on Blue Rubicon's advisory board for the past year.