The 20-foot boat that came ashore in Crescent City, north of San Francisco, had writing on it that was traced to a high school in Rikuzentakata, Japan.
The National Oceanic and Atmospheric Administration said it worked with the Japanese Consulate in San Francisco to officially identify the boat as belonging to Takata High School.
The boat is among the first debris from the tsunami to reach the North American coast.
The Los Angeles Times said the discovery had actually been investigated earlier in the month by a professor at Humboldt State University, who translated the writing and contacted Takata High on Facebook.
Takata was destroyed by the tidal wave, and some of its students and staff were killed, the Times said.