The Russian opposition politician is able to speak again, reports Der Spiegel magazine on Thursday.
Alexei Navalny is receiving treatment in Berlin’s Charite hospital after falling ill on a Russian domestic flight last month.
Germany says Navalny was the victim of an attempt to kill him and has demanded an explanation from Russia.
Moscow has said it has seen no evidence that Navalny, 44, was poisoned.
Der Spiegel magazine said Navalny's police protection had been stepped up in the expectation that he would be receiving more visitors as his condition improved.
"Der Spiegel and Bellingcat understand that Navalny can speak again and can likely remember details about his collapse," the magazine wrote, crediting its investigative website partner.
"His statements could be dangerous for people behind the attack."
There was no immediate comment by the hospital treating Navalny.