There are many historical sources that describe Yagi-jo Castle including "Taikoki" (Chronicle of Hideyoshi TOYOTOMI), "Akechi Gunki" (Biography of Mitsuhide AKECHI), "Tanba Fudoki" (Tanba Province Gazetteer), "Tanba Kohaiki" (The Rise and Fall of Tanba), "Momi-ke Nikki" (Diary of the Momi Family), "Naito Seisuiki" (The Rise and Fall of the Naito Clan), and "Yagi-cho Shi" (Yagi Town Journal").
八木城の記載されている史料は多く、『太閤記』『明智軍記』『丹波風土記』『丹波興廃記』『籾井家日記』『内藤盛衰記』『八木町誌』等がある。