The men, who include a Kuwaiti of Iraqi origin and two Syrians, were also convicted on Monday of forming an armed group with links to al-Qaida.
The court acquitted two defendants. The rest were sentenced to jail terms ranging from three months to four years, after the trial which began in March.
“Long live justice,” cried the two Yemenis who were acquitted.
Muhammad al-Azzam, the lawyer of the six convicted men, said he would appeal against the verdict.
“The evidence used to convict the men is not legitimate. This verdict is not fair,” he added.
Yemen, the ancestral homeland of al-Qaida leader Osama bin Laden, has cracked down on his supporters since the 11 September 2001 attacks on US cities and has cooperated closely with the US-led “war on terror”.
It has captured and sentenced several al-Qaida followers, including those behind the 2000 USS Cole bombing and the 2002 attack on the French supertanker Limburg.
The Yemeni court on Sunday also put on trial four Iraqis accused of plotting to carry out attacks on foreign interests in Yemen, on instruction from Saddam Hussein’s government.