In domestic policies especially, Yoshimoto displayed his uncommon abilities, starting with the enactment of the articles (Kana Mokuroku Tsuika) to expand on the 'Imagawa Kana Mokuroku' (the Imagawa clan's basic house rules to control the territory) in 1552, carrying out excellent administrative reforms such as commercial protection and distribution control within his territory, and consolidation of vassals by introducing the system of Yorioya-Yoriko (Later, when Ieyasu TOKUGAWA established the feudal government, he applied these policies to the system of the Edo bakufu.)
特に内政面において辣腕を振るい、天文22年（1552年）には「今川仮名目録」の追加法を制定し、さらに商業保護や流通統制、寄親寄子制度による家臣団の結束強化を図るなど優れた行政改革を進めた（後にこの政策は江戸幕府を開府した徳川家康によって踏襲されている）。