Bundestag speaker Wolfgang Schäuble, Germany's former hardline finance minister, disqualified the ballot of Petr Bystron of the anti-immigration Alternative for Germany (AfD) party and fined him $1,240 after the MP posted the image on Twitter.
“He knowingly violated the principle of the secrecy of the vote,” Schäuble told the chamber, calling it a “grave violation of the order and dignity of the Bundestag”.
Bystron had posted the photo apparently taken behind the curtain of the polling booth with the caption “Not my chancellor”.
Separately, an AfD member, Matthias Vogler, was removed from the viewing stands of the Bundestag for unfurling a banner reading “Merkel must go” during her swearing-in.
Merkel, bruised by half a year of post-election coalition haggling, was narrowly confirmed by parliament Wednesday to her fourth and likely final term at the helm of Europe's biggest economy.