He studied eonomics at the University of Nairobi, earning both a Bachelor of Arts in Economics and a Master of Arts in Economics from the university. His Doctor of Philosophy, also in economics, was obtained from the University of Gothenburg in Sweden.
He is the former Governor of the Central Bank of Kenya, a position he occupied for two consecutive four-year terms, from March 2007 until March 2015. Before his appointment as Governor of the Central Bank of Kenya, Ndung'u was the director of training at the African Economic Research Consortium. He has lectured in advanced economic theory and econometrics at the University of Nairobi, where he was an associate professor of economics.
Ndung'u has had extensive research and teaching work in various fields of economics, including macroeconomics, microeconomics, econometrics, and poverty reduction. A long-time researcher and trainer with the AERC and MEFMI network, he has published in international journals as well as chapters in various books on economic policy issues, inflation, interest rate and exchange rate issues, financial management, public sector growth, external debt, financial liberalization in Anglophone Africa, structural adjustment, as well as on employment and labour market issues.