Calmy-Rey established a small enterprise in the book distribution business. From 1981 to 1997 Calmy-Rey served as a representative in the Grand Conseil of the canton of Geneva as a member of the Social Democratic Party (PSS/SPS), and was president of the assembly during 1992–1993. She was president of the Geneva section of the party from 1986 to 1990 and again from 1993 to 1997. In 1997, Calmy-Rey was elected to the Conseil d'Etat of Geneva. In 2001, she became head of the Finance Department and president of the Conseil d'Etat of the canton.