Sager al-Hashash was sentenced in March 2013 to two years in prison by a court of first instance, before being released by a Court of Appeal, which had then reduced his sentence to one year.
The new verdict is final.
Mr. Hashash was sentenced for having put online in October 2012 tweets considered offensive to the emir when the opposition demonstrations to protest against an amendment to the electoral law animated.
Several opposition activists and former members have been convicted in recent years in prison for lyrics deemed offensive to the emir, Sheikh Sabah al-Ahmad al-Sabah.
Criticizing the emir is considered a breach of security was in Kuwait, and the guilty face up to five years in prison.