Hadar graduated from Hebrew University in Jerusalem and completed his graduate studies at Columbia University, where he earned M.A. degreees from the Columbia University Graduate School of Journalism and the School of International and Public Affairs as well as a certificate from the Middle East Institute. He received his Ph.D. from the School of International Service (SIS) at American University.

A former United Nations correspondent for the Jerusalem Post, Hadar is currently the Washington bureau chief for the Business Times (Singapore). He also taught political science at American University and Mount Vernon College, where he served as director of international studies, and was affiliated as a research fellow with the * EastWest Institute (formerly the Institute on East-West Security Studies), the * Center for International Development and Conflict Management(CIDCM) at the University of Maryland, College Park and the Independent Institute. Leon T. Hadar: The Independent Institute

Hadar's analyses on global affairs have appeared in newspapers, including The New York Times, The Washington Post, Washington Times, The Los Angeles Times, Christian Science Monitor, Chicago Tribune, Atlanta Journal and Constitution, The Baltimore Sun, The Philadelphia Inquirer, The Dallas Morning News, Houston Chronicle, The Orange County Register, El Pais, The Korea Herald, The Australian, Middle East Times, and Tehran Times as well as in magazines such as Columbia Journalism Review, Foreign Affairs, Foreign Policy, World Policy Journal, Current History, Middle East Journal, Journal of Palestine Studies, Washington Report on Middle East Affairs and * Mediterranean Quarterly. The broadcast outlets CNN, Fox News, CBC, BBC, NPR and VOA have interviewed him. He also contributes regularly to news websites published by such outlets like The Globalist, Antiwar.com, LewRockwell.com, Asia Times Online, The National Interest, * IRC Right Web Program, and Fox News.