"Similar statements, no matter where they come from, violate the truth and are completely inadmissible," said Andrei Nesterenko, a Russian Foreign Ministry spokesman.
Nesterenko's condemnation came after Ahmadinejad once again called the Holocaust "a lie" in a televised address Friday.
Ahmadinejad said the Holocaust, in which 6 million Jews died, was "a false pretext to create Israel" and urged Muslims to confront the "Zionist regime (as) a national and religious duty."
"Attempts to rewrite history, especially as the 70th anniversary of the start of World War II is being marked this year, are an offense to the memory of all victims and all those who fought fascism," Nesterenko said.
He also warned that Ahmadinejad's denial "does not contribute to creating an international atmosphere that would foster a fruitful dialogue on issues concerning Iran."