Vienna's highest court granted Irving's appeal and ruled to convert two-thirds of Irving's three-year sentence into probation, the Austria Press Agency reported. Since Irving has already spent more than 13 months behind bars, the ruling means he will be released from prison, according to APA.
In February, another Vienna court sentenced Irving to three years behind bars under a 1992 law, which applies to "whoever denies, grossly plays down, approves or tries to excuse the National Socialist genocide or other National Socialist crimes against humanity in a print publication, in broadcast or other media."
The law calls for a prison term of up to 10 years.
During his one-day trial earlier this year, Irving pleaded guilty to the charge of denying the Holocaust but maintained he never questioned it in the first place.
Both the defense and the prosecution appealed the sentence. In September, Austria's highest court upheld Irving's conviction.
Irving has been in custody in Austria since his November 2005 arrest on charges stemming from two speeches he gave in Austria in 1989 for which he was accused of denying the Nazis' extermination of 6 million Jews. He has contended that most of those who died at concentration camps like Auschwitz succumbed to diseases such as typhus rather than execution.
Irving was present at Wednesday's hearing and was brought into the packed courtroom in handcuffs.