However, the airline group said it expected the effect to have largely worn off by the end of December.
The group said the attacks "significantly impacted" traffic to and from Paris.
Before the attacks passenger numbers were higher than the same period last year, but then fell below that level.
In its monthly traffic update, Air France-KLM said: "The negative impact of the Paris attacks on total November revenues is estimated to be around €50m ($54m, £36m).
"Current booking trends are in line with a progressive recovery including a very limited impact on volumes after the end of December 2015.
Last week, Ryanair said it had cut fares in response to a dip in demand after the attacks, but said it did not expect the lower prices to have a material impact on its financial results.
Scandinavian carrier SAS also said it had seen a drop in travel to Paris and Brussels but that traffic was returning to normal.
