Ulster Bank was established in Belfast in 1836 as Ulster Banking Co and from the outset issued its own banknotes. Within a year it had 9 branches in Ulster and had appointed correspondent banks in London, Liverpool, Birmingham, Dublin and the United States of America. The branch network continued to grow, spreading into Leinster, the expanding Belfast suburbs and Munster. Staff shortages, caused by workers serving in uniform, led the bank to employ women for the first time in 1915.

Consolidation in the UK banking sector, combined with the political upheaval which followed the Easter Rising in 1916, prompted the takeover of Ulster Bank by London County & Westminster Bank in 1917. From the late 1920s the bank began to establish new services and departments, such as a Foreign Department in 1926 and thrift deposit accounts in 1928. However, the bank’s growth was limited after 1929 due to world depression and the collapse of the Belfast linen and shipbuilding industries. During the Second World War the bank suffered shortages and controls. Many staff enlisted, a number of Belfast branches were extensively damaged during air raids. The bank was called upon to handle clothing coupons, national savings certificates and transactions for US troops in Belfast.

In 1961 the management and capital of Ulster Bank was reorganised and a new board with defined functions and powers was appointed. During the 1960s many branches were renovated and new ones opened. Ulster Bank became the first Irish bank to introduce cash dispensers and the bank also set up merchant banking, factoring and unit trust management subsidiaries. In 1968 the new National Westminster Bank logo was adopted and in 1970 the Ulster Bank head office moved to Donegall Place.

During the 1970s the bank diversified into mobile banking, computer services, investment banking, offshore banking and dealing in the capital markets. During the 1980s problems caused by recession and competition had to be faced and in 1983 Ulster Bank became a private limited company under new company legislation. In the early 1990s expansion of branch network continued, particularly in the Republic of Ireland. A new head office was officially opened in Donegall Square East, Belfast, in 2000.

During 2001 Ulster Bank Group simplified its corporate structure by transferring its banking business in the Republic of Ireland to Ulster Bank Ireland Ltd. Meanwhile its growth continued in 2004 with the acquisition by The Royal Bank of Scotland Group of the Dublin-based mortgage and savings bank First Active plc.