Paris-based production company Les Films de l'Apres-Midi confirmed today that Karimi went to prison the previous day.
He was found guilty on charges of "insulting sanctities" in Iran in October 2015 and initially sentenced to six years behind bars.
He and his lawyer have said the charges stemmed from an unspecified video clip and a film he directed called "Writing on the City" that focuses on political graffiti in Iran from its 1979 Islamic Revolution to the contested 2009 election.