The government "reiterates its opposition to the death sentence, in all cases and all circumstances," said French foreign ministry spokesman Romain Nadal.
The French authorities "are fully mobilised to help Serge Atlaoui, whose situation remains very worrying," Nadal said in a statement, expressing his government's "solidarity" with the countries whose nationals were put to death.
Atlaoui, 51, was originally among the group set to be executed but was unexpectedly granted a temporary reprieve Saturday after Indonesia agreed to allow an outstanding legal appeal to run its course.
A Filipina woman who was set to suffer the same punishment was however spared at the 11th hour.
French President Francois Hollande has warned that Indonesia would face diplomatic "consequences" if it pushed ahead with the execution of Atlaoui over drug trafficking offences.