A spokeswoman from the airport, the fifth largest in Britain, told AFP the evacuation of the main terminal building was sparked by the discovery of a "suspicious item found in the security search area".
The spokeswoman said the entire terminal building had been emptied.
"All incoming flights have been suspended and the approach road to the airport has also been closed," the airport's press office added in a statement.
"The decision has been taken with the police to ensure the safety and security of passengers and staff.
Luton is London's fourth biggest airport in terms of passenger numbers after Heathrow, Gatwick and Stansted.
Total passenger traffic last year was around 9.7 million people.
