The ball was found by David Baxter on the shore of Middleton Island, south of the Alaskan mainland, the Kyodo news agency reported.
His Japanese wife Yumi translated writing on the ball as messages from Grade 3 school children in 2005 for a 16-year-old high school student in Iwate Prefecture, an inland region in northern Japan.
Kyodo contacted the teenager, Misaki Murakami, who confirmed he had owned the ball and couldn't find it after the tsunami.
There are increasing amounts of tsunami debris washing ashore in the United States and Canada, although the bulk of the "debris field" isn't expected to wash ashore until 2014, oceanographers have said.
Last month, in the Gulf of Alaska, the U.S. Coast Guard sank an abandoned 164-foot Japanese fishing boat cast adrift by the disaster as it was deemed a hazard to other ships.