The appeal, which opened at a court in the southern Bavarian city of Regensburg without Bishop Richard Williamson present, is the fifth round of court proceedings in the case.
"Bishop Williamson was not there, but he also didn't have to come," the judge Bettina Mielke said, adding the verdict was likely due on September 23.
The 73-year-old bishop was convicted of incitement to hatred after telling Swedish television in a 2009 broadcast that "200,000 to 300,000 Jews perished in Nazi concentration camps" and disputing the existence of Nazi gas chambers.
But the actual interview took place in Regensburg, where it is illegal to deny the Nazis murdered six million Jews during World War II.
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Two courts handed him fines, but these were later quashed due to procedural problems, before a further court fined him 1,800 euros (USD 2,378) in January.
While still a member of the breakaway ultra-conservative Catholic fraternity, the Society of Saint Pius X Society, Williamson also hit the headlines in 2009 when the then pope, Benedict XVI, reversed his excommunication in a bid to bridge a rift with the organisation.
Williamson was expelled from the fraternity of traditionalists last year after it said he had disobeyed and disrespected his superiors for several years.