The court in the city of Meknes sentenced Mohamed Baassou for the harassment offence as well as "insult to modesty," but dismissed a charge of human trafficking, Hassan Bennajeh, a leader of Al Adl Wal Ihsane, told AFP.
In addition to his jail time, the court ordered Baassou to pay 60,000 dirhams ($6,000) to the complainant.
Bennajeh said Baassou's sentencing "only confirms that he was targeted for the group he belongs to and his opinions."
Aicha El Guella, the lawyer for the complainant, said Baassou "took advantage of the vulnerability of his victim by promising work in order to achieve his ends. The investigation found that he used the same technique with other women."
Al Adl Wal Ihsane (Justice and Dignity) seeks a state under sharia Islamic law but rejects any violence in pursuit of that goal. The group is tolerated but unrecognized by Moroccan authorities.
Several journalists and others in Morocco have also been sentenced for sex-related offences over the past few years. They denied the accusations and said they were targeted for their views.
Moroccan authorities say such cases have nothing to do with freedom of expression and the kingdom's judiciary is independent.