The rejection of his candidacy, which was condemned by ultranationalist party leaders as undemocratic, can be challenged at the constitutional court.
Georgescu surprisingly won the first round of the presidential election in Romania on November 24.
Shortly before the run-off, the constitutional court cancelled the first round due to irregularities in campaign financing.
The election will be repeated on May 4.
Georgescu registered his candidacy with the electoral commission on Friday.
He had submitted 324,000 declarations of support, more than the 200,000 required according to the law.
According to media reports, the electoral commission justified its rejection, saying some submitted documents were incomplete.
Dozens of supporters of Georgescu gathered outside the election bureau shouting "Freedom" and briefly tried to force their way through the security cordon.
Romania's highest court annulled the ballot two days before the second round of voting in December, citing allegations of Russian government interference in Georgescu's favour, which the Kremlin has denied.
Members of US President Donald Trump's administration called Romania's cancelled election an example of European governments suppressing freedom of speech and political opponents.
Tech billionaire and Trump adviser Elon Musk called the election authority's decision "crazy" on his social media platform X.
Georgescu is under criminal investigation on six counts, including membership in a fascist organisation and communicating false information about campaign financing.
He has denied all wrongdoing.
Georgescu supports the Romanian Orthodox Church and has sparked controversy in the past for describing Romanian fascist and nationalist leaders from the 1930s and 1940s as national heroes.
According to local media, he has praised Russian President Vladimir Putin as "a man who loves his country" but he claims not to be pro-Russian.
The electoral commission on Sunday made its decision against Georgescu in a vote of 10 to 4, Romanian media reported.
The constitutional court must decide on an any appeal from Georgescu by Wednesday.
with DPA and AP
29°C