Csanad Szegedi, a member of the European parliament and regional leader of Jobbik, said he learned "not long ago that I had parents of Jewish origins, that's the big news.
"I'm not saying I wasn't surprised by this news," he added, noting it would take a while to "digest" the information.
Mr Szegedi has repeatedly used anti-Semitic rhetoric in the past and also got attention when in 2009 he attended the first session of the European parliament in a uniform of the Hungarian Guard, a paramilitary branch of Jobbik which has since been banned.
In his latest interview he noted however: "I think that what counts is not to know who is a pure race Hungarian, the important thing is the way one behaves as a Hungarian.
"To be Hungarian for me has always been a responsibility (towards my country), that has nothing to do with racial supremacy."
Another Jobbik deputy recently made headlines after he asked a laboratory to test that he did not have Roma or Jewish genes.
Szegedi's news on Wednesday gave way to amused, as well as cutting reactions on social networking sites.
Members of Jewish organizations joked about the revelations, urging rabbis to invite Mr Szegedi to their synagogue for prayers.
One blog, Narancs. Hirado, meanwhile observed that it was "impossible that Szegedi had not known his grandmother Magoldna Klein was Jewish and a Holocaust survivor."