The Belgian attacker has signed a four-year deal to play in Ligue 1.
The Addicks were linked with a move for the Lokeren player all summer. Earlier this month the Sevenoaks Chronicle reported on the news. They claimed Charlton were keen on the player, who had a €750,000 (£538,000) release clause in his current deal in Belgium.
Chalrton have a good record with recruiting from Belgium in recent times, thanks mainly to their Belgian chairman Roland Duchatelet.
On this occasion however they have missed out.
It was confirmed yesterday by the official club website of En Avant Guingamp that De Pauw had agreed a switch to France instead.
They stated that the flying winger had signed a four-year deal at the Ligue 1 side but did not reveal how much they paid for the player.
Charlton will be disappointed to have missed out on what seemed to be a much wanted commodity at the club.
Now they will need to move on and explore different wide options as they get set for yet another tough Championship campaign.