Duo allegedly asked for €3 million in exchange for not publishing a damaging book about the king, reported France 24.
The journalists who sought money have been identified as Eric Laurent and Catherine Graciet.
They were arrested on Thursday after meeting with a representative of the Moroccan government in a Paris restaurant.
Moroccan palace officials were contacted by these two journalists on July 23 informing them that they had written a book on Mohammed VI, and a first meeting was organised in Paris with a Moroccan lawyer.
The Moroccan government informed French authorities about the blackmailer journalists and a further meeting took place, this time under police surveillance.
"Both Eric Laurent and Catherine Graciet were present. They signed a contract and received 80,000 euros in cash" said Dupond-Moretti a lawyer of the king.
Both were arrested as they left the establishment "with the proceeds of their crime in their pockets", the lawyer said.