Declan Costello was born in Galway, Ireland in 1967. He has a Degree in Economics from Trinity College Dublin and a Masters' Degree from the College of Europe in Bruges. He joined the European Commission in 1991 and has worked in DG ECFIN (barring a 9 month secondment to the Portuguese Ministry of Finance) as an economist up until 2012. During the 1990s, he was actively involved in preparations to launch the euro, including the setting up of the Stability and Growth Pact (SGP). Once EMU was launched in 1999, he worked on fiscal policy issues, especially on population ageing and the sustainability of public finances.
He was a Head of Unit for 8 years, managing various units dealing with economic analysis on labour markets, social security systems and growth policies under the Lisbon, and subsequently, 2020 strategy. Since the onset of the economic crisis, he has actively been involved in efforts to devise an economic recovery strategy, as well as negotiations on economic governance in EMU especially on competitiveness and macroeconomic imbalances. He has also been involved in some of the economic adjustment programmes, notably Greece.
From 2012 to 2014, he was acting Director for Resources and Communication in ECFIN. From 2014 to September 2015 he was Director for the Economies of the Member States, covering nine Member States (Germany, Austria, Cyprus, Greece, the Netherlands, Czech Republic, Slovak Republic, Croatia and Spain) responsible for forecasting economic developments and prospects, and for monitoring compliance with the requirements of the Stability and Growth Pact and the Macroeconomic Imbalances Procedure. He was also Mission Chief for the European Commission's team working on Greece. In October 2015, he was appointed Principal Adviser and the European Commission's Mission Chief for Greece for the Third Economic Adjustment Programme.