Former high school teacher Gerald Frederick Toben, 64, was refused bail in London's Westminster Magistrate's court and will appear again on Friday for an extradition hearing, Australia's ABC Radio reported.
Toben was arrested under a European Union arrest warrant because he is wanted by the District Court in Mannheim, Germany, on charges of publishing material on the internet of an anti-Semitic and/or revisionist nature.
Denying the Holocaust is an offense in Germany with a maximum jail term of five years.
In 1999, Toben spent seven months in jail in Germany and has served an 11-month sentence in Austria for Holocaust denial.
In 2006, Toben was a speaker at a controversial two-day conference in Tehran organized by the Iranian government and attended by President Mahmoud Ahmadinejad. There, he described as "mere puffery" the assertion that Jews were killed by the Nazis.