The company utilizes a team-based investment approach and has focused exclusively on fixed-income securities since its founding in 1971.

Western Asset Management Company was founded in October 1971 by United California Bank (which later became First Interstate), and became an SEC-registered investment advisor in December of that year.

Now known as Western Asset Management Company Limited, it operates as the firm’s London office.

[citation needed] In December 2003, the fixed-income division of Rothschild Asset Management (Singapore) Limited was acquired by Legg Mason and merged into the existing operation.

To further develop Western Asset's capabilities and global presence, Legg Mason acquired a substantial part of Citigroup's asset management business in exchange for its brokerage and capital markets business.