He began his career as an assistant lecturer at Nairobi University in 1978. He joined the Central Bank of Kenya in 1980 and worked his way through the ranks from an Economist to Director of Research.

He also worked as an economist on a fixed term appointment with the International Monetary Fund (IMF) 1985 - 1990, after which he returned back to the Central Bank of Kenya.

He was appointed Financial Secretary to the Treasury in June 1995, a position he held until July 1999 when he rejoined the Central Bank of Kenya as Director of Financial Markets. In October 2000, he was appointed the Chief Economist of the Central Bank of Kenya.

He was appointed as the Permanent Secretary, Ministry of Finance in September 2002, a position he held until January 2003 when he was appointed Permanent Secretary in the Ministry of Planning and National Development.

In July 2003 he was appointed Permanent Secretary in the Ministry of Agriculture where he served until July 2004 when he was reappointed Permanent Secretary to the Ministry of Finance where is currently engaged.

Mr. Kinyua has also served as Director on several boards of State Corporations. He is also a member of the Programme Committee of the African Economie Research Consortium (AERC) and Alternate Governor, World Bank Board of Governors

Academics
He holds BA(Econ.) and MA(Econ.) degrees from Nairobi University