"I dedicate my entire contribution to this film to honest and courageous people across the world who day after day find the strength to confront the monster of dictatorship and its constant companion, war," Navalny said on Twitter.
"I am, of course, terribly glad, but while rejoicing, I try not to forget that it wasn't me who won the Oscar," he said.
He thanked the team who made the movie inlcuding Canadian director Daniel Roher, Navalny's long-time ally Maria Pevchikh and Bellingcat investigative journalist Christo Grozev.
Navalny also thanked his wife Yulia, who was in Hollywood for the Oscars ceremony on Sunday.
He was arrested in January 2021 upon returning from Germany, where he had recovered from the infamous poison attack.
The 46-year-old learned about the film prize from his lawyer, who told him via video-link during a court case.
"I had a very strange feeling at that moment," Navalny said.
"It was as if those words didn't even belong in this world, but, on the other hand, everything here is so weird and crazy that it feels like that's the only world they belong in."
Navalny has frequently criticised the Ukraine offensive from prison and called on Russians to protest.
Recently, he called for the respect of Ukraine's borders of 1991, which include the Crimean peninsula annexed by Moscow in 2014.
Asked about the award, Kremlin spokesman Dmitry Peskov said Hollywood "politicises" the cinema industry.