Irving told reporters he was very shocked by the sentence, handed down after he pleaded guilty to the charge, which stemmed from a 1989 speech and interview in which he denied that gas chambers were used at the Nazi concentration camp Auschwitz.
The comments were made in Austria, one of 11 countries with laws against denying the Holocaust.
"I consider the verdict a little too stringent. I would say it's a bit of a message trial," said defence lawyer Elmar Kresbach.
Jewish leaders have welcomed Irving's conviction, although some have questioned whether his three-year sentence will make him a martyr.
Change of heart
However Mr Irving insisted during his one-day trial that he has had a change of heart and now acknowledged the Nazis' World War II slaughter of six million Jews.
In particular he conceded he had erred in contending there were no gas chambers at the Auschwitz concentration camp.
"I made a mistake when I said there were no gas chambers at Auschwitz," Mr Irving testified, at one point expressing sorrow "for all the innocent people who died during the Second World War."
Before the verdict he told journalists he considered it "ridiculous" that he was standing trial for remarks made 17 years ago.
Handcuffed and wearing a navy blue suit, he arrived at court carrying a copy of one of his most controversial books ‘Hitler's War’, which challenges the extent of the Holocaust.
Mr Irving's trial was held amid new and fierce debate over freedom of expression in Europe, where the printing and reprinting of unflattering cartoons of the prophet Mohammed has triggered violent protests worldwide.
Past views
In the past, however, he has claimed that Adolf Hitler knew little if anything about the Holocaust, and has been quoted as saying there was "not one shred of evidence" the Nazis carried out their "Final Solution" to exterminate the Jewish population on such a massive scale.
Mr Irving, the author of nearly 30 books, has contended most of those who died at concentration camps such as Auschwitz succumbed to diseases such as typhus rather than execution.
Renouf shows support
Former Australian beauty queen and controversial London socialite, Michele Renouf, turned up at the Vienna court to support British historian David Irving.
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Lady Michele Renouf, the third wife of the late New Zealand financier Sir Frank Renouf, has long been an advocate of right-wing views.
Arriving in court she made her views plain to assembled media, calling for the bodies of "so-called Holocaust victims to be exhumed to see whether they died from typhoid or gas".
She praised Mr Irving for "standing up to the Zionists" before a member of the Austrian press shouted at her "Do you think your British flag entitles you to bring your Nazi propaganda into this court?"