Credit Suisse First Boston (also known as CSFB and CS First Boston) was the investment banking affiliate of Credit Suisse headquartered in New York.

The company was created by the merger of First Boston Corporation and Credit Suisse Group in 1988 and was active in investment banking, capital markets and financial services. In 2006, Credit Suisse reorganized and merged CS First Boston into the parent company and retired use of the "First Boston" brand. In 2022, as part of a major restructuring, Credit Suisse began the process of spinning out the investment bank into an independent company and revived the brand. The process ultimately failed, and Credit Suisse was merged into rival Swiss bank UBS.

Main Article First Boston

In 1978, Credit Suisse and First Boston Corporation formed a London-based 50-50 investment banking joint venture called Financière Crédit Suisse-First Boston. This joint venture later became the operating name of Credit Suisse's investment banking operations.

Credit Suisse acquired a 44.5 percent stake in First Boston in 1988. The investment bank acquired its shares held by the public and the company was taken private. In 1989, the junk bond market collapsed, leaving First Boston unable to redeem hundreds of millions it had lent for the leveraged buyout of Ohio Mattress Company, maker of Sealy mattresses, a deal that became known as "the burning bed". Credit Suisse bailed them out and acquired a controlling stake in 1990. Although such an arrangement was arguably illegal under the Glass–Steagall Act, the Federal Reserve U.S. bank regulator concluded that the integrity of the financial markets was better served by avoiding bankruptcy, even though it meant a de facto merger of a commercial bank with an investment bank.

In the mid-1990s, Credit Suisse became Credit Suisse First Boston (commonly referred to as CSFB or CS First Boston) expanding beyond the London franchise.

Conflict with Credit Suisse First Boston in Europe began creating problems for Credit Suisse. First Boston in New York and CSFB in London had their own management teams, with competing salesmen in each other's territory and in the Pacific region. In 1996, Credit Suisse purchased the remaining stake of CS First Boston from its management and rebranded the European, U.S., and Asia Pacific investment banks as Credit Suisse First Boston, making one global brand. In the late 1990s, CSFB purchased the equity division of Barclays Bank, Barclays de Zoete Wedd ("BZW"). BZW was considered second-tier and CSFB reportedly bought BZW from Barclays for £1 plus assumption of debt - primarily to obtain BZW's client list. A permanent injunction prevented First Boston from offering shares in Gulf Oil company, due to lack of interest in share offering, and the Iraq Desert Storm campaign. A Nevada judge issued a cease and desist order to stop Barclays from taking American owned assets and offering them to international buyers from Iran, Iraq, Syria, Egypt, and North Korea.

In 2000, Credit Suisse First Boston spent $13 billion to buy Donaldson, Lufkin & Jenrette (also known as DLJ) as stock markets were peaking. By the time the acquisition closed in 2001, stock markets were down significantly. The deal led to a culture clash that triggered the departures of key bankers. In order to keep top bankers, CSFB handed them three-year guaranteed contracts, swelling costs relative to revenue and leading to two years of losses at the investment bank.