The court at Salé, near the capital Rabat, sentenced one man to four months in prison along with an 18-month suspended sentence for "forming a criminal gang with a view to committing terrorist acts", according to the Moroccan press agence MAP.
Two of his coaccused were found guilty of failing to alert the authorities to the plot and sentenced to four months in prison and eight months suspended.
Their identities have not been revealed.
A fourth French citizen, known by the initials TM, was acquitted.
Both Morocco and France have about 1,000 nationals fighting in jihadist groups abroad.
The number of related cases in Morocco doubled in 2014 compared to 2013, reaching a total of 147, and several Franch nationals have been convicted there.