Also known as: 小津城, 小戸城

A branch of Matsukura Castle, built in 1335 by the Shiina Clan, the castle was taken over by the Uesugi Clan during the Sengoku. It then became a strategic castle for the Uesugi for control of Ecchuu, and Kawada Nagachika served as its chamberlain for many years. In 1582, the castle was surrounded by Oda troops led by Shibata Katsuie, Sassa Narimasa, Maeda Toshiie, and Sakuma Morimasa. A fierce battle and siege ensued, (the Battle of Uozu Castle), and the castle finally fell when 13 of Uesugi's commanders committed ritual suicide. However, the Oda army immediately withdrew after hearing of the death of Oda Nobunaga at Honnou Temple. In 1583, Sassa Narimasa again laid siege to the castle, and Suda Mitsuchika surrendered to him, ending Uesugi control of the castle.

After Narimasa, the castle passed into the hands of the Maeda Clan, but was destroyed under the "One Province One Castle" decree of the Tokugawa Shogunate.

Oomachi Elementary School as well as a courthouse now stand on the former site of the castle, of which very few traces remain.