Former Breakaway Resources managing director and mining engineer Victor Rajasooriar has been appointed as chief operating officer.
Louis Mostert has joined Barminco as general counsel and company secretary.
He was most recently general counsel for London-listed AMEC and previously with GRD until its takeover by AMEC.
Former Seven West Media general manager of finance Michael Ellis has been appointed as financial controller.
"We are delighted to have filled these three positions with high quality candidates," Barminco CEO Peter Stokes said.
"I look forward to working with Victor, Louis, and Michael and drawing on their experience as we grow the business."