"It's clear that this step will follow," Petry said as quoted by Spiegel Online and other media outlets. The party leader didn't specify when exactly she would leave.
The news comes after Petry announced at the AfD's Bundestag press conference on Monday that she would not be a member of the party in the parliament, but rather an independent MP, in order to pursue "realpolitik in the best sense of conservative policy."
Following the announcement, AfD's leading candidate for the Bundestag Alice Weidel called on Petry to leave the party "to prevent further harm."
The AfD was the biggest winner in Sunday's elections, entering the Bundestag for the first time with 12.6% of the vote as Germany's main parties suffered historic losses.
Petry has been co-chair and spokesperson for AfD at the federal level since 2015. She shares her duties with Joerg Meuthen.
