From 1989 to 1991 he was chairman of European Democrat Students, while from 1997 to 2001 Papastavrou was chairperson of the
Democrat Youth Community of Europe. He was a candidate in 1999 Euro-elections with
New Democracy but not elected. In 2004 when Nea Demokratia won the national elections in Greece, Prime Minister
Kostas Karamanlis appointed him International Secretary of
New Democracy, the centre-right party of Greece. At the Euroelections of June 2009 he was again a candidate, this time ranked 9, but his party Nea Demokratia elected only 8. After the elections of 2009 the new leader of Nea Demokratia Antonis Samaras re-appointed him as International Secretary, a position he held until 2015. Following the
June 2012 election, the newly appointed
Prime Minister of Greece,
Antonis Samaras, appointed him as his Deputy Chief of Staff for European and International Affairs at the Prime Minister's Office. In August 2012 he was appointed Coordinator of the Greek German Partnership, the bilateral cooperation among the Greek and German state aiming to exchange of technical expertise in various public domains. Following the win of New Democracy in the
June 2023 Greek legislative election, Papastavrou was appointed Minister of State. His mandate included the coordination of the ministries' activities for attracting major investments, the supervision of the Special Secretariat of Foresight, and the supervision of the Coordinating Mechanism for the Rights of People with Disabilities. On 14 March 2025 he was appointed Minister of Environment and Energy. ==Offshore connections==