Filin, 42, suffered third-degree burns to his face and eyes last January when a masked assailant threw concentrated acid in his face outside his Moscow apartment building.
Dmitrichenko, 29, was arrested in March when police said he confessed to organizing the attack, however, Dmitrichenko insisted he did not know the perpetrator planned to use acid.
RAPSI reported Dmitrichenko entered his plea during the first day of his trial Tuesday.
Yury Zarutsky, the alleged assailant, pleaded guilty to carrying out the attack, but said he acted alone. Andrei Lipatov, who allegedly drove Zarutsky to Filin's apartment, pleaded not guilty, the legal news agency said.
Filin has suggested the goal of the attack may have been to remove him from his position as artistic director of the theater, but investigators have also said the motive might have been revenge because Filin passed over Dmitrichenko's girlfriend for roles in the theater's ballets, RAPSI said.