Chan served as Singapore's Permanent Representative to the United Nations from 1989 to 1991. During this time, she was concurrently accredited as the High Commissioner to Canada and Ambassador to Mexico. She became the Ambassador to the United States in 1996. At the time, she was the first woman ambassador from an East Asian country to be assigned to the United States. Chan expressed surprise at her appointment, noting "I'm anti-establishment and was a bit of a dissident before I was appointed ambassador. It came as something of a shock to me when I was offered the ambassadorship because I was highly critical of government in a society that is not used to being critiqued."