Bahar (Spring) was ordered shut for "publishing false material, spreading doubt on key issues like the elections, questioning the decisions of regime officials and spreading lies about ministries," the watchdog said, quoted by Fars.
The newspaper had resumed operations in February, after being shut down in 2003 by the judiciary.
"Since the paper continued to break the law in its issues over the past two months, it was decided to suspend its publication and refer it to the judiciary," the watchdog said.
Iran's press watchdog has since last year banned several publications, mostly reformist journals, for breaching its strict regulations.
Authorities have come down hard on the media and arrested scores of journalists since anti-government protests erupted after President Mahmoud Ahmadinejad's disputed re-election in June 2009.
His victory bitterly divided Iran's political elite amid persistent allegations the election was massively rigged in his favour.
Since Ahmadinejad's first term, authorities have generally cracked down on the media, mostly from the reformist camp, but some conservative publications have also faced closures.
