A regular in the National League Team of the Weekend despite Barrow’s struggles, he rejected a new deal to stay with the Bluebirds last month.
Dover have been looking for a central defender since they lost Manny Parry to Boreham Wood.
The towering Frenchman has solved the issue - the 6f 5in centre-half was a former Paris Saint-Germain youth player.
He is the second player to swap the Cumbrian coast for the Kent coast. Bedsente Gomis signed for Chris Kinnear earlier this month.
Diarra is Kinnear’s fourth signing of the summer with Kevin Lokko and striker Inih Effiong also joining.
“Diarra arrived in the UK in 2011 and played for St Albans City before moving to Hemel Hempstead and then winning promotion from the Ryman League with Hampton & Richmond Borough,” read the Dover website’s announcement.
“Welcome to Crabble Moussa!”