"After November 1, I will no longer exercise my functions, and I reject any extension of my mandate," the 71- year-old said in a letter read out to parliament in the Kurdish capital Arbil, a copy of which was obtained by AFP.
"Changing the law on the presidency of Kurdistan or prolonging the presidential term is not acceptable," said the architect of the September 25 independence vote, which led to the Kurds losing to Baghdad's forces disputed territory to which they laid claim.
Barzani also said he would continue "remain a peshmerga (Kurdish fighter) among the ranks of the people of Kurdistan and I will continue to defend the achievements of the people of Kurdistan".
Sunday's parliamentary session was held behind closed doors because of "sensitive questions" that would be discussed, deputies said earlier.
Officials from Barzani's Kurdistan Democratic Party (KDP) had told journalists ahead of the session that the letter to be read out would announce he was stepping aside.