Two men got two years in jail and the third was sentenced to 15 months.
The Gothenburg District Court says Monday the case involved two Palestinians and a Syrian.
The 22-year-old Palestinian had his asylum application turned down following the December 9 attack and will be deported after serving his sentence. The others, aged 19 and 24, have Swedish residency permits.
The court said they were part of a masked group who threw burning objects at the synagogue, which the prosecution said was a reaction to the US decision to recognize Jerusalem as Israel's capital.
All three pleaded innocent. They were the only people charged.