Nagashima played baseball at his local high school, and on the Rikkyo University baseball team from 1954–1957. He joined the Yomiuri Giants in 1958. His jersey number (3) is now a retired number for the Yomiuri Giants. After retiring, he became manager of the Yomiuri Giants from 1975–1980, and again from 1993–2001. He was scheduled to manage the Japanese national team for the 2004 Athens Olympics, but he suffered a stroke shortly before and was hospitalized.