He was the sixth person to be sentenced to a significant prison term in cases stemming from a wave of anti-Kremlin protests in Moscow this summer.
Aleksandr Pal, a film actor, started the campaign to support Ustinov, calling it a flash mob, and invited other actors to join.
"This is a completely trumped-up case," Pal said in his video statement, referring to Ustinov by a nickname. "From the video of his arrest it is clear that Pasha wasn't resisting national guard servicemen and riot police, that he wasn't chanting any slogans."
Pal's call was picked up by Nikita Efremov, an actor with Moscow's Sovremennik theater and a member of a famed family of actors.
"I remember well the case of Ivan Golunov, I was amazed by how journalists got united," he said in a video, adding "I think we can do that too."
In June, Golunov, a prominent Russian investigative reporter, was arrested in central Moscow and charged with drug trafficking. The arrest swiftly prompted protests by journalists and their supporters, who picketed the Moscow police headquarters. In a stunning reversal, the charges were dropped days later, and several high-ranking police officers were fired.
"In terms of corporate solidarity, this is not the first time it is being expressed," Ekaterina Schulmann, a political scientist in Moscow and a member of President Vladimir Putin's Council for Civil Society and Human Rights, told Kommersant, a Russian newspaper. "Any unity is an effective instrument."
Golunov's case raised hopes of a new Kremlin flexibility in the face of public outrage. But weeks later, police began making mass arrests during the street protests in Moscow — more than 2,000 overall.
Speaking to reporters on Tuesday, Putin's spokesman, Dmitri Peskov, repeated his usual line that the Kremlin had nothing to do with the court system and that Ustinov had the right to appeal if he disagreed with the sentence.
"Of course, the president is aware and received all information about everything," Peskov said. "However, the president also cannot either react or influence the court's decision."
Replicating the slogan used by Golunov's supporters, many actors posted "I/We are Pavel Ustinov" on their social networks.
Just as in the Golunov case, the show of support for Ustinov spread to some Kremlin-friendly commentators, including Tina Kandelaki, a television producer, and Maksim Galkin, a popular television host and comedian.
"This is a huge reputational blow," Galkin said. "This is a blow to our courts, and not the first one," he said, adding, "this is a blow to our government too."
Nikita Kukushkin, an actor with the Gogol Center, an avant-garde theater in Moscow, made a plea for actors to stop working with the government and "feeding this system."
"I call on you not to cooperate with film companies, producers, and directors that offer you projects that are clearly propaganda," Kukushkin said. "Don't take part in productions or put on plays in theaters that were given to directors only because they expressed their loyalty to the government."
Several leading theaters in Moscow, including Satirikon, made statements in support of Ustinov at the ends of their shows on Monday.
"It turned unbearable to remain silent," said Yulia Snigir, a popular film actress. "You cannot put an innocent man in jail."
Written by: Ivan Nechepurenko
© 2019 THE NEW YORK TIMES