"I have just been informed that I have been deprived of the right to enter the Russian Federation for five years," Zingeris said at a news conference on Thursday.
The lawmaker said that the Kremlin's decision derailed his plans to go to Moscow to collect material on the murder of the Russian opposition leader, adding that he will now have to do so remotely.
"Let's hope that Moscow will not take steps to derail the report itself," he said.
Vladimir Kara-Murza, a Russian opposition politician and journalist, described Moscow's decision as "unprecedented behavior", which basically shows that Russia's authorities are responsible for the killing of Nemtsov.
"This is an admission of guilt," he said.
Nemtsov was shot dead on a bridge near the Kremlin on February 27, 2015.
Five men have been convicted in the assassination, but Nemtsov’s family and supporters believe the real masterminds of the murder have escaped justice.