CSB was founded on 26 November 1920, well before Indian independence, and opened for business on January 1st, 1921 with an authorized capital of Rs.5 lakhs and a paid up capital of Rs. 45270/- During the first two decades of its functioning, the Bank concentrated only in Kerala. Banks and credit institutions which proliferated especially in Kerala received a jolt and many of them came to their doom following the crash of the Travancore National Quilon Bank in 1938 followed by Palai Central Bank in 1960. During the period many small banks came to the verge of collapse shaking the confidence of the public and what followed was a process of consolidation. The strategy of mergers and amalgamations of small banks with bigger banks brought the number of banks within controllable limits, thereby making the industry's base strong. In 1964-65, The Catholic Syrian Bank Ltd took part in taking over the liabilities and assets of five small/medium sized banks in Kerala. The expansion programme initiated during these years gathered momentum in the subsequent years. In August 1969, the Bank was included in the Second Schedule to the Reserve Bank of India Act 1934.
At present, The Catholic Syrian Bank Limited (CSB) is an Indian private sector bank with its headquarters at Thrissur, Kerala, India. It is one of the oldest banks in India. The bank has a network of over 420 branches and more than 240 ATMs across India.  At a very early stage, the Bank recognized mechanization as an effective tool of management and streamlined its accounting procedures by introduction of Data processing system. From November 1975, reconciliation of inter-branch accounts was mechanized by using IBM Data processing machines. The decade of the seventies saw the evolution of a new culture in Indian Banking. Nationalization of banks imposed "Social Control" and imparted new ethos to commercial banking . What followed was a massive expansion of bank branches with a distinct thrust on remote rural belts. Special schemes were formulated to cater to the diverse credit needs of small scale industries, road transport operators, agriculturists,and other self employed entrepreneurs.