The man identified by his initials N.R., who was under police restrictions in France, was picked up yesterday at Casablanca airport, the Moroccan interior ministry said in a statement.
He was detained along with his two girls, aged two and four, and a Moroccan woman with whom he had a "traditional" marriage, said the statement, cited by the local MAPP news agency.
His legal wife, a French national, was said to have remained in France.
The man was said to have been on his way to Turkey when he was arrested.
IS fighters are involved in heavy fighting just across the Turkish border in Syria.
Over 2,000 Moroccan jihadists, including those with dual nationality, are currently fighting in Syria and Iraq, according to Rabat.
Moroccan authorities fear some will return and attempt to carry out attacks at home and has announced heightened security measures, notably at the borders.
