The three Islamic Central Council of Switzerland (ICCS) suspects included the group's head Nicolas Blancho and spokesman Qaasim Illi, who were both acquitted.
But German national Naim Cherni, the head of the council's "culture production department", was sentenced. He had travelled to Syria in 2015 and made films there with a known Islamist leader. Abdallah Al-Muhaysini of the jihad umbrella organisation Jaysh al-Fath ("Army of Conquest").
The films, which prosecutors say amounted to jihadist propaganda, were "promoted via social media and at a public event" by Blancho, Illi and Cherni, they had said.
Blancho, who converted to Islam at age 16, has in the past denied being tied to extremism but has staked out positions considered more radical than other Muslim leaders in Switzerland.
The ICCS has previously said that the videos Cherni made in Syria have "nothing to do with Al-Qaeda" and were intended to raise awareness among Muslims about the conflict in the country.
In an email to AFP earlier, Illi said the attorney general was "pushed by an Islamophobic social wave (and) is trying to defame Switzerland's largest Islamic grassroots organisation by its fabricated claim."
He said the ICCS had nearly 4,000 members, representing about one percent of Muslims in Switzerland.
The Syrian conflict has claimed more than 350,000 lives and displaced millions since 2011.
Editors' correction: The original headline of this article stated Naim Cherni had been jailed. This is not the case. He has been handed a suspended sentence.