Nomura Securities Co., Ltd. is a wholly owned subsidiary of Nomura Holdings, Inc. (NHI), which forms part of the Nomura Group. NSC plays a central role in the securities business, the Group's core business. Established December 25, 1925 in Osaka, it is the oldest brokerage firm in Japan. It is named after its founder Tokushichi Nomura II, a wealthy Japanese stockbroking tycoon.

NSC provides a range of services through the capital markets including trading, brokerage, underwriting, offering, secondary offering and private placement of securities.

Nomura makes most of its profits in the Japanese retail banking market, but has expanded its international investment banking capabilities. Instinet Incorporated was acquired in February 2007.

In October 2008, Nomura acquired most of Lehman Brothers Asian operations together with its European equities and investment banking units to make one of the world's largest independent investment banks with Y20,300bn (£138bn) assets under management according to the Financial Times.

In April 2009, the global headquarters for investment banking was moved out of Tokyo to London as part of a stated aim by Hiromi Yamaji, Nomura’s chief executive of global investment banking to move the company's focus from Japan to global markets.

Nomura sponsors research at Oxford University into mathematical techniques for use in finance including stochastic analysis, option pricing, stochastic optimal control, interest rate modelling and through the Nomura Centre for Mathematical Finance.