The defence is entitled to petition for a final appellate review by the Supreme Court within 30 days.
"The two defendants are leading figures with political experience who knew that their opinions could sway the public, yet they have repeatedly aired their malicious views via television although the judiciary has granted a number of opportunities for remorse and reform," the Court of Appeals said in its verdict.
The high court said it found no cause to grant leniency in the sentencing.
As talk show hosts, Samak and Dusit were convicted by the Criminal Court for defamation against former deputy Bangkok governor Samart Ratchapholsit.
The two insinuated that Samart was linked to bidding irregularities in 2006. Their last year's conviction involved four counts of making libel remarks against Samart. For each count they were punished to serve six months in jail.
Samart said he would file a civil suit demanding Bt100 million following the completion of the appellate process.
Samak refused to talk to reporters.