In our study, we present a conceptual model of Social Responsibility for the banking sector, which aims at providing an ideal framework to represent the overall aspects that a bank should consider, when really committed toward society and the environment. The effectiveness of Corporate Social Responsibility (CSR) is directly related to its degree of integration into the corporate governance and management system. Sustainability needs to be pro-actively recognized by the corporate bodies and should permeate the services and products of a bank. Analysing the main official guidelines on sustainability provided for the financial sector, we build up a comprehensive model to analyse the state of the art of sustainable financial products and services, as well as the general sustainability trajectories that have been recently undertaken by banks. Within the banking sector, the approach adopted by cooperative banks on the Social Responsibility discourse shows substantial differences compared with other banks. Cooperative banks, in fact, strictly integrate solidarity, cooperation and localism statutory principles into their overall organization. Conventional methods to assess CSR performances are unable to capture the big effort made by cooperative banking toward ‘sustainability’. By introducing the idea of ‘implicit’ Corporate Social Responsibility, the study proposes a way to overcome this limitation. Recognising the local approach as well as the stability of relationships in cooperative banking, the CSR debate has been focused on the multifaceted concept of Social Capital. The conclusions report different measures of Social Capital.