The court convicted Semena, 66, on separatism charges and handed down a 2.5-year suspended sentence and a ban on future journalistic activity, RFE/RL said.
"This conviction was based on the fact that Mr. Semena had criticized Russia’s occupation and attempted annexation of Crimea in his writing," U.S. State Department spokeswoman Heather Nauert said in a statement.
"We call on the Russian occupation authorities to vacate Mr. Semena's conviction, allow him to resume his journalistic activity, and cease their campaign to stifle dissent in Crimea," she said.
Read alsoOSCE media watchdog condemns journalist Semena's conviction in occupied Crimea (Video)"Crimea remains an integral part of Ukraine, and the United States remains steadfast in its support for the territorial integrity and sovereignty of Ukraine," she said.
Semena, a contributor to RFE/RL's Krym.Realii (Crimea Realities), was arrested on April 19, 2016, by Russia-imposed authorities and charged with acting against the "territorial integrity of the Russian Federation."