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In financial services, a broker-dealer is a natural person, company or other organization that engages in the business of trading securities for its own account or on behalf of its customers. Broker-dealers are at the heart of the securities and derivatives trading process.

Although many broker-dealers are "independent" firms solely involved in broker-dealer services, many others are business units or subsidiaries of commercial banks, investment banks or investment companies.

When executing trade orders on behalf of a customer, the institution is said to be acting as a broker. When executing trades for its own account, the institution is said to be acting as a dealer. Securities bought from clients or other firms in the capacity of dealer may be sold to clients or other firms acting again in the capacity of dealer, or they may become a part of the firm's holdings.

In addition to execution of securities transactions, broker-dealers are also the main sellers and distributors of mutual fund shares.

In the United States, broker-dealers are regulated under the Securities Exchange Act of 1934 by the Securities and Exchange Commission (SEC), a unit of the U.S. government. All brokers and dealers that are registered with the SEC (pursuant to 15 U.S.C. § 78o), with a number of exceptions, are required to be members of the Securities Investor Protection Corporation (SIPC) (pursuant to 15 U.S.C. § 78ccc) and are subject to its regulations. Some regulatory authority is further delegated to the Financial Industry Regulatory Authority (FINRA), a self-regulatory organization. Many states also regulate broker-dealers under separate state securities laws (called "blue sky laws").

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