Sanneh was born in Gambia, and studied at a number of institutions throughout the world, including the University of London, where he received a Ph.D. in Islamic History. He has written a number number of books and articles on the relationship between Islam and Christianity, including Faith and Power: Christianity and Islam in “Secular” Britain, The Crown and the Turban: Muslims and West African Pluralism, and Piety and Power: Muslims and Christians in West Africa. Sanneh converted to Christianity from Islam.

Another major area of Sanneh's academic work is in the study of World Christianity. He writes extensively about the translation of the Christian message, challenging a good deal of the accepted history of mission in the modern academy. In his 1989 Translating the Message, he writes:

In time, Christianity expanded from Europe into Asia and Africa, among other places, and was able to break out of its Western cultural confinement by repeating the process by which the church's missionary center shifted from Jerusalem to Antioch and beyond. In some important respects, however, the modern shift was unprecedented, for it was the extraordinary multiplicity of mother-tongue idioms that became the subject of Christian mission rather than the cosmopolitan values of an ascendant West. Nonetheless, mission maintained continuity with its apostolic past. In examining the modern missionary phase, however, we should highlight important signposts in the indigenous culture, especially in the local encounter with the modern West. The translation role of missionaries cast them as unwitting allies of mother-tongue speakers and as relucant opponents of colonial domination.

He extends these historical reflections further in his 2008 Disciples of All Nations.

As a professor, Sanneh has taught and worked at the University of Ghana, the University of Aberdeen in Scotland, Harvard, and (since 1989) at Yale. He is an editor-at-large of The Christian Century, and serves on the board of several other journals. According to the Yale University Website, "He is an Honorary Research Professor at the School of Oriental and African Studies In the University of London, and is a life member of Clare Hall, Cambridge University. He serves on the board of Ethics and Public Policy at Harvard University, and the Birmingham Civil Rights Institute in Birmingham, Alabama." Sanneh is also a Commandeur de l'Ordre National du Lion, Senegal's highest national honor. He is a member of the Pontifical Commission of the Historical Sciences and of the Pontifical Commission on Religious Relations with Muslims. Sanneh is a naturalized United States citizen.

His wife, Sandra Sanneh, is a professor of isiZulu at Yale University. Their son, Kelefa Sanneh writes about culture for The New Yorker.

?Translating the Message: The Missionary Impact on Culture. Maryknoll, New York: Orbis Books, 1989.?The Jakhanke Muslim Clerics: A Religious & Historical Study of Islam in Senegambia (c. 1250-1905). Lanham, Md.: University Press of America, January 1990.?West African Christianity: The Religious Impact. London: Christopher Hurst, George Allen and Unwin; Maryknoll: Orbis Books, 1983.?Encountering the West: Christianity & the Global Cultural Process: The African Dimension, London: HarperCollins Publishers; Maryknoll, New York: Orbis Books, 1993.?The Crown and the Turban: Muslims and West African Pluralism. Westview Press. Imprint of HarperCollins. October, 1997.?Religion and the Variety of Culture: A Study in Origin and Practice. Valley Forge, PA.: Trinity Press International, 1996.?Het Evangelie is Niet Los Verkrijgbaar, Uitgeverij Kok. Kampen, Netherlands: 1996.?Piety and Power: Muslims and Christians in West Africa. Orbis Books, October 1996.?Faith and Power: Christianity and Islam in 'Secular' Britain (with Lesslie Newbigin & Jenny Taylor), London: SPCK, 1998.?Abolitionists Abroad: American Blacks and the Making of Modern West Africa, Cambridge, MA: Harvard University Press, 2000.?Whose Religion is Christianity?: The Gospel Beyond the West, Grand Rapids: Eerdmans, 2003. (Winner: Theologos Award for "Best General Interest Book 2004")?The Changing Face of Christianity: Africa, the West, and the World (co-edited with Joel A. Carpenter). Oxford: Oxford University Press, 2005.?Disciples of All Nations: Pillars of World Christianity. Oxford: Oxford University Press, 2008.