Kostas Christidis is a distinguished alumnus of Varvakeios Model School and a graduate of the Law School of the University of Athens and the London School of Economics (M.Sc. in Economics, specializing in Accounting and Finance). An attorney at the Athens Bar Association (1973-2008), he has extensive experience as a legal and financial advisor for numerous public and private sector entities.

He has served as President or Vice President on boards including Macedonian Spinning Mills S.A., Duty-Free Shops S.A., and the Hellenic Cadastre Organization. He has authored or co-authored seven books on political and economic issues and is a regular columnist in Estia.