Kashima Nagamasa served as a bushō during the Sengoku period.  Nagamasa was the first head of the Kashima family serving as chief retainers of the Awa-Tokushima domain.

His father, Kashima Nagashige, served as a retainer of Imagawa Yoshimoto, the sengoku daimyō of Suruga Province.  After a dispute with Yoshimoto, Nagashige departed Suruga and entered into service for Oda Nobunaga in Owari Province.  Similar to his father, Nagamasa also served Nobunaga.  For his contributions on the battlefield, he received landholdings in Owari and Mino provinces.

In 1582, Nobunaga unexpectedly died in a coup d’état known as the Honnō Temple Incident.  Nagamasa’s wife, Narahime, was the daughter of Hachisuka Masakatsu.  In 1585, Nagamasa relied upon his wife’s older brother, Hachisuka Iemasa, to go to Awa Province in Shikoku.  He was then granted landholdings of 10,000 koku and delegated Tokushima Castle.

Nagamasa died on 7/4 of Tenshō 16 (1588).