Crosses were broken and tombstones overturned in the Guebwiller Franco-German cemetery in the Alsace region. The vandalism affected 95 tombs. An offensive message was written on at least one of the tombs, the Haut-Rhin departmental police authority said, without giving further details.
President Nicolas Sarkozy wrote a letter to his German counterpart Horst Köhler, denouncing the desecrations as "revolting and cowardly", the French presidential palace said.
A total of 1,238 German soldiers and as many French are buried in the cemetery, in a region that was controlled by Germany for half a century until the end of World War I.
France's Defence Minister Herve Morin told AFP after visiting the cemetery on Friday that the vandalism was an "insult to the memory of those who died in the two world wars".
"It is an insult to all that we have built after the European wars, a country of peace and stability based on reconciliation and Franco-German friendship," he said.