The court in the southern city of Gwangju found Kim Kyung-Il guilty of professional negligence resulting in death, a court spokesman said by phone.
Prosecutors said Kim, whose vessel was the first on the scene as the Sewol listed and sank, bore responsibility for the botched rescue effort that wasted precious time and delayed the evacuation of passengers from the stricken ferry.
He was also charged with making a false report that he had broadcast an evacuation order through loudspeakers.
The tragedy - blamed by many on regulatory failings, official incompetence and the ship's illegal redesign - plunged the nation into a lengthy period of mourning.
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The official response to the disaster was widely criticised for being slow, uncoordinated and unfocused, and prompted President Park Geun-Hye to vow a complete overhaul of national safety standards.
More than 50 people have been put on trial on charges linked to the sinking, including 15 crew members who were among the first to climb into lifeboats.