Yoshinori Yokoyama first had a position in the Kunio Maekawa & Associates. He later joined Davis, Broady & Associates in 1973. Yokoyama joined McKinsey in 1975. He served as a Director at McKinsey from 1987 to 2002. Yokoyama also served as a Senior Fellow at the Research Institute of Economy, Trade and Industry, IAI from 2002 to 2004. Yokoyama was appointed as an Auditor to the Industrial Revitalization Corporation of Japan in April 2003. In June 2006, Yokoyama was appointed an Outside Director at Sumitomo Mitsui Financial Group and Sumitomo Mitsui Banking Corporation.

Yokoyama first became a member of ORIX Corporation's Advisory Board in June 1997 before becoming a Director in June 2002. Yokoyama became an Outside Director under a "Company with Committees" structure in June 2003.

Yokoyama was born in 1942.