Yanada Mochisuke served as a bushō during the Sengoku and Azuchi-Momoyama periods.  He was a retainer of the branch of the Ashikaga clan serving as the Koga kubō.  Mochisuke served as the lord of Seikyado and Mizuumi castles in Shimōsa Province.  He was the great-great-grandchild of an individual by the same name from the Muromachi period.

In 1549, Mochisuke was born as the son of Yanada Harusuke.  In 1567, Mochisuke inherited the headship of the clan following the entry by Harusuke into the priesthood.

At the time, Harusuke did not recognize Ashikaga Yoshiuji as the Koga kubō (who was backed by the Gohōjō clan).  Instead, he supported Ashikaga Fujiuji who relied upon the Satomi clan.  With the support of Uesugi Kenshin and Satake Yoshishige, he fervently resisted the Hōjō army.  In 1574, Sekiyado Castle was finally toppled and, even though Harusuke and Mochisuke were rescued, they were banished to the auxiliary site of Mizuumi Castle.  Based on continuing assistance from the Satake clan, Mochisuke resisted but was later persuaded by Ashikaga Yoshiuji to serve as the head of senior retainers in Yoshiuji’s domain.

In 1582, after the death of Yoshiuji, Mochisuke served as the steward at his funeral but soon thereafter Sekiyado Castle was seized by a faction of the Yanada family supporting the Hōjō so Mochisuke came into conflict with the Hōjō again.

Mochisuke died in 1587.