"The staff member in question was detained following allegations by a passenger travelling on flight MH20 from Kuala Lumpur to Paris on August 4 of inappropriate sexual behaviour by a member of the cabin crew," Malaysia Airlines said in a statement.
"Malaysia Airlines expects and accepts nothing short of the highest standards of conduct from its crew and takes any such allegations very seriously," it said.
"We will naturally assist the French authorities as they conduct their investigation and would stress that the safety, comfort and well-being of our passengers is always our highest priority," the airline said.
The incident supposedly happened when the passenger expressed nervousness about flying following the disappearance of flight Malaysia Airlines MH370 in March and the downing of flight Malaysia Airlines MH17 in July, the Star Online reported.
Malaysia Airlines Flight MH370 disappeared mysteriously in March with 239 people, including five Indians on board after taking off from Kuala Lumpur on March 8.
On July 17, MH17 was shot down over Ukraine, with 298 people killed.