According to his younger brother Hesham, they had eight siblings. Hesham remembers his older brother "as a happy-go-lucky guy, and something of a womanizer." Born in Saudi Arabia, Zubaydah moved to the West Bank as a teenager, where he joined in Palestinian demonstrations against the Israelis. Zubaydah is reported to have studied computer science in Mysore, India prior to his travel to Afghanistan/Pakistan at the age of 20 in 1991. He joined the mujahideen in the Afghan civil war, perhaps serving under Mohamad Kamal Elzahabi. In 1992, Zubaydah was injured in a mortar shell blast, which left shrapnel in his head and caused severe memory loss, as well as the loss of the ability to speak for over one year.