Al-Timimi was born in 1963 and grew up in Washington, DC, where he attended Georgetown Day School until age fifteen. His father was an attorney who worked at the Iraqi embassy, and his mother was a mental health specialist with a doctorate in psychology. One of Al-Timimi's teenage friends was the son of journalist Milton Viorst, who later wrote in The Atlantic that the family was "not particularly ethnic or religious," and that Al-Timimi celebrated holidays such as Halloween and Christmas with his brother and other friends at school. Viorst writes that Al-Timimi's parents were both practicing Muslims, but spoke English rather than Arabic at home and "did not push religious observance on the children."