A state security court convicted the defendant for "creating a page on a social network under his own name to spread false information and ideas, and to mock and damage the reputation and status of state institutions," said the official news agency WAM.
Media in the United Arab Emirates identified the man as Osama Hussain al-Najjar.
Serving a 10-year term, his father was among dozens of Islamists convicted last year for membership of Al-Islah Society, viewed as the UAE branch of the Muslim Brotherhood.
Local media said the son had used Twitter and Facebook to spread information.
He was charged with "contacting foreign organisations and providing false information on the conditions of convicts" imprisoned for their links to Al-Islah.
Najjar will also have to pay a 500,000-dirham ($136,124) fine under the ruling, which is final.
Amnesty International swiftly condemned the sentencing, which it said showed "the UAE's "intolerance for dissent".
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"With this vindictive conviction following a charade of a trial, the UAE authorities have again made crystal clear that when they don’t like the message, their first line of defence is to smear and silence the messenger," said Boumedouha, Amnesty's deputy regional head.
"The trial and conviction of Osama al-Najjar shows the hollowness of repeated government assertions that the UAE conducts fair trials," said Boumedouha.
The UAE this month released a long list of what it branded "terrorist organisations", topped by Al-Islah and the Muslim Brotherhood.
Amnesty on November 18 released a report entitled "There is no freedom here: Silencing dissent in the UAE."
The rights watchdog spoke of a "climate of fear" and the "extreme lengths" taken by authorities to stamp out opposition or calls for reform.
Abu Dhabi has criticised the report as "one-sided and inaccurate", insisting it was committed to improving the protection of human rights.
The UAE has not seen any of the pro-reform protests that have swept other Arab countries since 2011, including fellow Gulf states Bahrain and Oman.
But authorities have stepped up a crackdown on dissent and calls for democratic reform.