The state of emergency will continue for a period of 30 days, but can be lifted any time during this period, according to an announcement made by the prime minister's office.
Under the decree, the security forces are given wider powers to deal with criminal elements.
The announcement came late on Sunday, after the Jamaica Constabulary Force reported several looting incidents across the island.
The situation will be reviewed at an emergency meeting of the Jamaican cabinet on Monday, said Prime Minister Portia Simpson Miller.
The meeting, the prime minister said, will be to ensure "that apart from all the things that have already been in place, I think we will now have to assess and move speedily to ensure we can get things back to normality."
As reports came in of blocked roads, downed power lines, ripped-off roofs and flooding, Miller hinted that the national elections set for 27th August may be delayed to deal with the hurricane damage.
The category four hurricane was whipping up giant surf and dumping inches of rain on the island.
Roads were blocked by fallen trees and flooded in the eastern parts of the island, with power cuts affecting thousands of homes. - DDNEWS
