Ždanoka was a long-standing member of the European Parliament, having first been elected in 2004, and was seen as one of the most pro-Kremlin MEPs in the chamber. But this year she quit Brussels to become a candidate for a Russian nationalist party, the Latvian Russian Union.
The decision comes after a court ruling found that Ždanoka was an active member of the Communist Party, while the Saeima Election Law prohibits persons who after January 13, 1991 were participants in the Communist Party or the pro-Communist Interfront movement to run in Latvian elections.
The Central Election Committee had earlier asked for information over Ždanoka's candidacy from the Security Police and the Constitution Protection Bureau.
Ždanoka was the Latvian Russian Union party's #1 ticket for the Vidzeme cultural region.
But it was known previously she was likely be barred from the election, which might give her an opportunity to publicize the "oppression" of Russians and more specifically herself in Latvia, which is a popular theme with the Russian government of which she has been a staunch supporter.
The electoral body earlier found seven candidates ineligible under the Saeima Election Law.