Siraj Wahhaj was born as Jeffrey Kearse and raised in Brooklyn. His mother was a nurse and his father a hospital dietitian. His brother is writer and editor Gregory S. Kearse of Silver Spring, Maryland. He went to church religiously and went on to become a Sunday school teacher as a teenager in a Baptist church.[4] Wahhaj then later went on to the New York University on a partial scholarship. He also played basketball where he met a teammate who interested him in the Nation of Islam, an African-American movement. He subsequently converted to Islam.

In 1969 he ended his schooling and joined the Nation of Islam, changing his name to Jeffrey12x.[4] During this time he was vocal in his belief that “white people are devils." He said of this, “I preached it. I taught it.”[5] Wahhaj says of his interest in the Nation: "It wasn't the theology that attracted me to the Nation of Islam at all... It was the kind of do-for-self black pride."

When Elijah Muhammed died in 1975, "His teachings began to unravel in my mind", and he became a Sunni Muslim with the encouragement of Muhammad's son Warith Deen Mohammed. Mohammed took over and reorganized the Nation of Islam, urging members to come to orthodox Islam. Kearse then changed his name again to Siraj Wahhaj, which means "bright light" in Arabic. He was chosen to study Islam at the Umm al-Qura university of Mecca for a period of four months in 1978.[5] He also briefly taught a course in Islamic studies at Howard University, where Johari Abdul-Malik is the chaplain.