Onaran completed his graduate degree in public administration at Middle Eastern Technical University in 1990. The same year, he began working at Garanti Bank, serving as the deputy inspector for the Inspection Board. He served as Regional Director for several Garanti Bank headquarters around Istanbul. With the establishment of Garanti Mortgage, Garanti Bank’s subsidiary responsible for the government of mortgage activites,  Onaran became the Executive Director. Onaran served as the Executive Director of Garanti Emeklilik and Hayat A.S. between 2012-2016. Since January 2016, Onaran is the Vice President of SME Banking at Garanti Bank.