As the closest relative to Iesada TOKUGAWA, the 13th shogun who did not have an heir, Iemochi became the 14th shogun at the age of thirteen, supported by Naosuke II, Fudai Hitto and others in the Nanki group (the group that supported Yoshitomi from the Kishu-Tokugawa family).
徳川氏中、世継ぎのいなかった第13代将軍・徳川家定に最も近い血筋の人物であるとして、譜代筆頭の井伊直弼ら南紀派の支持を受けて13歳で第14代将軍となる。