Petra Karin Kelly was born in Guenzburg, Bavaria, then in West Germany, in 1947. She attended the Englisches Institut, a Catholic girl’s boarding school, until 1960, when she went to Columbus, Georgia, with her mother and stepfather, U.S. Army Lieutenant Colonel John E. Kelly. In Georgia she became involved in civil rights activities, while simultaneously learning English. She attended high school in Hampton, Virginia where she had a weekly radio program on current issues.

In 1966 she entered the School of International Service at American University in Washington, D.C.; majored in political science, international relations, and world politics; and graduated cum laude with a B.A. in 1970. She won a Woodrow Wilson National Fellowship and served as a teaching assistant for one year. She was active in student government and foreign student affairs at American University and initiated its first International Week in 1966, which has become an annual tradition. As a student active in the anti-war, civil rights, anti-nuclear, and feminist movements-she worked as a volunteer for Senator Robert F. Kennedy's 1968 presidential campaign, founding Students for Kennedy in Washington. After Kennedy's assassination she worked as a volunteer in the office of Senator Hubert H. Humphrey, helping his electoral campaign, becoming his friend and the recipient of many letters on political subjects and requests for advice on European questions. She recalls, "After supporting the civil rights and anti-war movements in Georgia, Virginia, and Washington, D.C., I became very much a nonviolent activist after 1968."