The lower court has ordered that the three be jailed immediately but police did not arrest them
The former MPs were charged with undermining the status of the emir during an address at a public gathering on October 10 in which they warned that any amendment to the electoral law could lead to street protests.
Kuwait later saw protests at which demonstrators said an amendment to the electoral law allowed the government to influence election results and elect a rubber-stamp assembly.
The opposition boycotted a December 1 general election in protest at the amended law.
The lower court sentence sparked peaceful street protests and dozens of youth activists have staged sit-ins every night since in protest against jail terms on Twitter users and activists.
So far, Kuwaiti courts have given jail terms of between two and ten years to at least four opposition tweeters for allegedly insulting the emir. Many more are on trial on similar charges.
Opec member Kuwait, which produces around 3.0 million barrels of oil per day, has been rocked by ongoing political disputes since mid-2006 that have stalled development despite abundant surpluses.