Amnesty International criticised the sentence handed down to Nasser bin Ghaith, calling it "another devastating blow for freedom of expression in the United Arab Emirates."
Ghaith has been held after tweeting criticism of Egypt, an ally of the UAE, which is a federation of seven sheikhdoms on the Arabian Peninsula.
A report on the state-run WAM news agency said Ghaith was convicted of "communicating with secret organisations linked to the Muslim Brotherhood," as well as making "offensive" online posts.
The UAE, while liberal in many regards compared to its Middle Eastern neighbors, has strict laws governing expression.