Riaz was born in 1972 to an aristocratic Muslim family in Faridpur District, Bangladesh. Riaz is the youngest child in his family. He has six sisters and a brother, Raisuddin Ahamed Siddique. He was brought up in CNB staff quarters of Faridpur for the first sixteen years of his life.[5] His father, the late Zainuddin Ahamed Siddique, was a government service holder. His mother was Arjumand Ara Begum. His paternal home is in Jessore District. His father died in 1988. After the death of his father, Riaz moved to Jessore district in 1989.

Riaz took the exams to be a pilot in the Bangladesh Air Force (BAF) right after his HSC results. From then on, he became a top-rate fighter pilot. He underwent training in Turkish Air Force on a scholarship for one-and-a-half years. He enrolled at the BAF Academy from 1989 to 1991 for flying training and to earn his bachelor's degree under Rajshahi University in science, he was commissioned as a Pilot Officer in Bangladesh Air Force in 1991. However, he was later dismissed from the Air Force due to a misunderstanding with the authorities.

After being dismissed from the BAF, Riaz moved to Dhaka in 1994. There he met his cousin, actress Bobita, and started his film career in 1995. Riaz married Mushfika Tina, a dance teacher, in a traditional Muslim wedding ceremony on 18 December 2007.