Born a photographer, Abbas is an Iranian transplanted to Paris. He has dedicated himself to documenting the political and social life of societies in conflict. In his major work since 1970 he has covered wars and revolutions in Biafra, Bangladesh, Northern Ireland, Vietnam, the Middle East, Chile, Cuba, and South Africa during apartheid.
From 1978 to 1980, Abbas photographed the revolution in Iran, to which he returned in 1997 after seventeen years of voluntary exile. His book Iran Diary 1971-2002 is a critical interpretation of Iranian history, photographed and written as a private journal.
During his years of exile Abbas traveled constantly. Between 1983 and 1986 he journeyed through Mexico, attempting to photograph a country as a novelist might write about it. The resulting exhibition and book, Return to Mexico: Journeys Beyond the Mask, helped define his photographic aesthetic.
From 1987 to 1994, he focused on the resurgence of Islam throughout the world. Allah O Akbar: A Journey Through Militant Islam, the subsequent book and exhibition, spanning twenty-nine countries and four continents, attracted special attention after the 9/11 attacks by Islamic jihadists. A later book, Faces of Christianity: A Photographic Journey (2000), and touring show explored Christianity as a political, ritual and spiritual phenomenon
Abbas' concern with religion led him in 2000 to begin a project on animism, in which he sought to discover why non-rational ritual has re-emerged in a world increasingly defined by science and technology. He abandoned this undertaking in 2002, on the first anniversary of 9/11, to start a new long-term project about the clash of religions, defined as culture rather than faith, which he believes are turning into political ideologies and therefore one of the sources of the strategic struggles of the contemporary world.
From 2008 to 2010 Abbas travelled the world of Buddhism, photographing with the same sceptical eye. In 2013 he concluded a similar long term project on Hinduism, after which he started working on Judaism around the world.
A member of Sipa from 1971 to 1973, then of Gamma from 1974 to 1980, Abbas joined Magnum Photos in 1981 and became a member in 1985.