During the Zedillo administration, she served as the country's first female secretary of foreign affairs (January 1998 to November 2000). In 2000 she signed a joint declaration for cooperation in the war against drug-trafficking with Igor Ivanov, the head of Russian Foreign Affairs. She represented Zedillo at the ceremony of change of government of Macau when sovereignty changed from Portugal to the Chinese government. She was also involved in the negotiations for the Free Trade Agreement between Mexico and the European Union.
During the Vicente Fox administration, she served as Mexico's ambassador to Argentina. On 30 September 2005, Green succeeded Elba Esther Gordillo as general secretary of the PRI. In the general election of 2 July 2006, she was elected to the Senate as the number-one candidate on the PRI's PR list.
Rosario Green was the first director (2005–2006) and visiting professor of the Kozmetsky Center for Excellence in Global Finance at St. Edward's University in Austin, Texas, U.S.[citation needed]