When Bonham Carter was five, her mother had a serious nervous breakdown, from which it took her three years to recover.
Njen oče, Raymond Bonham Carter, je bil trgovec in bankir, v šestdesetih pa je deloval kot vodja banke v Washingtonu, D.C.. Prihaja iz vplivne politične družine in je sin liberalnega politika sira Mauricea Bonhama Carterja ter priznane političarke in govornice Violet Bonham Carter.