After completing his military service as a reserve officer at the submarine base of Toulon, Danjean passed an examination to join the French DGSE as a civil servant.

Danjean later worked as a Balkans specialist for the Ministry of Defence and took part to the negotiations of the Rambouillet Agreement in February and March 1999.

In 2005, Danjean joined the staff of Minister of Foreign Affairs Michel Barnier where he was in charge of the Balkans and Afghanistan.

Danjain first became a Member of the European Parliament in 2009 for the East France constituency on the list headed by Joseph Daul.

[3] In 2010, he joined the "Friends of the EEAS", an unofficial and independent pressure group formed because of concerns that the High Representative of the Union for Foreign Affairs and Security Policy Catherine Ashton was not paying sufficient attention to the Parliament and was sharing too little information on the formation of the European External Action Service.

[8] Within the centre-right European People's Party Group (EPP), Danjean was from then on a member of the leadership team around chairman Manfred Weber.

[12] In 2015, Danjean warned fellow French conservatives against being soft on Russia, arguing that "through the fascination for Putin, there is a real philosophical and ideological pull-back, namely a rejection of political liberalism.

"[13] In The Republicans' 2016 presidential primaries, Danjean endorsed Alain Juppé as the party's candidate for the office of President of France.