Jan Kees de Jager was born on February 10, 1969 in Kapelle, in the province Zeeland.  He successfully completed the study Business Administration at the University of Nyenrode. In Rotterdam he graduated at Erasmus University in Economics with honors and Dutch law. During his studies he co-founded the Internet company ISM eCompany. For his contribution to this successful company and his work at the National Innovation Council and various ICT and innovative activities he received in 2006 the ICT Personality Award of the industry association ICT ~ Office.

February 2007 he was asked by Prime Minister Jan Peter Balkenende as Secretary of Finance in the cabinet Balkenende IV. In his tax plans De Jager focused on encouraging innovation, stimulating entrepreneurship, simplifying taxes and introducing a green tax system. In February 2010 he became Minister of Finance. And in October 2010 he continued this position in the cabinet Rutte I. With the euro crisis and difficult budget and economic conditions he was as Finance Minister at the center of the crisis. After the fall of the cabinet Rutte during the coalition budget talks in 2012 De Jager took the initiative to establish an emergency budget in consultation with five political parties. This resulted in the so-called Spring Agreement, in which a large number of reforms and budget cuts were agreed to save the 2013 budget. On his retirement in November 2012 he was the most popular minister.

After six intensive and challenging years of politics De Jager returns back to business. While setting up a new development center in Sri Lanka for his company ISM eCompany he was active as an entrepreneur with different business activities and as a frequent speaker. In September 2014 he started his current challenge as a member of the Board of Management of KPN in which he assumed the position of Chief Financial Officer in November of that year.