He was born in Beirut on October 14, 1933. He is married to Roseanne Khalaf and has two children. Khalaf has written extensively on the Arab world and on Lebanon in particular. The majority of themes in his work include sexuality in the Arab world, the Lebanese Civil War, Urbanization, and the role of the Protestantmissionaries in the Levant. Until 2017, he was a professor of sociology at the American University of Beirut, and has also been a director of the Centre for Behavioural Research there since 1994. He retired in 2017, keeping a part-time teaching position at the University. 
Khalaf received his bachelor's degree in Economics from the American University of Beirut in 1955, and later his MA in Sociology in 1957. Furthermore, he obtained an MA in Economics and Sociology in 1959, and PhD in Sociology in 1964 from Princeton University.