In 1858, Matsudaira Yoshinaga (better known as Matsudaira Shungaku) was forced into retirement during the Ansei Purge, and Naokiyo was transferred to Fukui Domain and was adopted as Yoshinaga's successor.

Also, Shōgun Tokugawa Iemochi granted him a kanji from his name, which then became Matsudaira Mochiaki.

However, he was mostly a figurehead within Fukui Domain, as the retired Matsudaira Yoshinaga continued to exert much influence, and all of the powerful retainers of the domain, including Yuri Kimimasa, Yokoi Shōnan, etc.

In June 1869, he defected to the side of the new Meiji government and was appointed imperial governor of Fukui, a post which he held to the abolition of the han system in 1871.

His son, Matsudaira Yasutaka (1867–1930) served as a member of the House of Peers of the Diet of Japan and was author of a number of works on agricultural science, having studied for several years in England.