The man, who is reportedly of Algerian origin, was arrested late on Saturday after a tip-off from a member of the public who saw a weapon in a car boot at the airport.
Other members of the man's family have been taken in for questioning, and the man himself can be held for up to four days without charge.
Paris police have made several arrests in the past two weeks of suspected Islamic militants who, the authorities says, were planning an attack on the Russian embassy in the city.
Family arrests
The man is reportedly a 27-year-old of Algerian origin, who lives in the northern Parisian suburb of Bondy.
He has no criminal record, say police.
As a baggage handler, he has security clearance for several areas of Charles de Gaulle airport, one of Europe's busiest.
Anti-terrorist officers have been brought in, but only as observers at present.
The man's father, two brothers and a family friend were also arrested, after the man's flat was searched.
An automatic pistol, a machine gun, five pieces of plastic explosive and two detonators were found in his car, according to police.
The British "shoe bomber", Richard Reid, boarded a flight to Miami from Charles de Gaulle with explosives hidden in his trainers a year ago.
Security effort
Police said before Christmas that they had found bomb-making equipment during raids on at least one of the addresses searched in the Paris suburbs.
In total, nine arrests have been made since 16 December, when four people were arrested in the Paris suburb of La Courneuve.
All those arrested are said to be of Algerian or Moroccan origin.
The arrests stem from an investigation into possible connections between Islamic militants in Europe and Chechnya.
Fearing a possible attack over the Christmas and New Year holiday period, the French Government has ordered an extra 1,000 police and troops on to the streets of Paris.
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