When the clubs merged, in time for the 2003–04 season, Red Boys was languishing in the bottom half of the Division of Honour, while AS was in mid-table position in the third tier of Luxembourgish football.

However, as Olympiakos Volou was presumably involved in a corruption case, UEFA decided on 11 August 2011 that Differdange would progress to the play-off round and meet Paris Saint-Germain, the furthest a club from Luxembourg has reached in European competitions.

Michel Leflochmoan was appointed as new coach as he is familiar in BGL League: with the F91 Dudelange and with Jeunesse Esch he won multiple championships in Luxembourg.

And on 25 July 2013 the made a 3–3 draw against Utrecht in the return, eliminating the Dutch club, which is significantly larger than Differdange, in the UEFA Europa League.

They won one match in Europe, winning their 1979 UEFA European Cup first leg 2–1 against Omonia Nicosia before losing 6–1 in Cyprus.