Samaha was also stripped of his civil rights which means that he will not be able to take any official government post or vote in elections.
He may be transferred to another prison at a later time.
He was charged with the possession of explosives for the purpose of carrying out terrorist attacks.
The verdict cannot be appealed.
The minister had previously served four-and-a-half years in jail as part of a lighter sentence that had shocked the country and which saw his release from prison earlier this year.
In accordance with Lebanese law, a prison year is counted as nine months meaning that Samaha will have to serve six years and nine months after counting the time he has already spent in jail.
The years Samaha already served will be deducted from the new sentence.
The new sentence was praised by anti-Syrian politicians.
“Terrorist Samaha will return to jail today which is the natural place for whoever plans to kill civilians,” former Prime Minister Saad Hariri wrote on Twitter.
The court rejected claims that the former minister was lured into devising the terrorist plot by informant Milad Kfouri.
Samaha had said he was a victim of entrapment because he was not aware that his co-conspirator was a Lebanese security services informer.
The presiding judge said that Samaha already had the intent to carry out his terrorist attacks and the only reason he was stopped was because Kfouri had reported him to the authorities.
Video recordings of Samaha and Kfouri in which he discusses his plot emerged as damning evidence against the official.
The ex-minister of information and close ally of Syrian President Bashar Assad , Samaha, 67, was arrested in August 2012 and charged with attempting to carry out “terrorist acts” over allegations that he and Syrian security services chief Ali Mamluk transported explosives and planned attacks and assassinations of political and religious figures in Lebanon.
Samaha was sentenced in May 2015 to four-and-half years in prison, but in June the Military Court of Cassation nullified the verdict and ordered a retrial.
Surprisingly, the court agreed in January to release Samaha on a $100,000 bail. He was banned from leaving the country pending a retrial.
Hezbollah ‘s parliamentary bloc chief MP Mohammed Raad defended Samaha’s release on bail and slammed as “malicious, temperamental and non-objective” the statements that criticized the release.
But Justice Minister Ashraf Rifi, , lashed out at the judicial and security officials for the decision to release Samaha. His release prompted Rifi to quit the cabinet