This thesis investigates possible approaches to social impact measurement in the context of corporate social responsibility initiatives and highlights possible challenges as well as the role of stakeholder interest. This is done by adopting a view focused on the social effectiveness for the beneficiaries of such initiatives, which is contrasting the hitherto existing way of evaluating impact predominately focused on internal and economic factors. Social impact-oriented corporate citizenship programmes of Deutsche Post DHL Group are chosen as a case study building the basis for the thesis. Information is collected in three in-depth semi-structured interviews with a company representative and two experts in the field and document analysis of corporate sustainability reports. The findings are discussed with the help of a theoretical framework based on stakeholder and legitimacy theory and qualitative characteristics for holistic impact measurement. The findings suggest that the development of appropriate tools and methods for (social) impact measurement is highly customised and adapted to the specific goals and intended outcomes of an intervention. Predefined and standardised measurement approaches, however, seem to have limited relevance and applicability. Moreover, effective measurement is especially feasible on an individual outcome level, while the social impact on a societal scale can only be achieved and summarised in an abstract and qualitative manner. In collaboration with its partners, Deutsche Post DHL Group appears to be strongly concerned about the effectiveness of its programmes and views impact measurement as an important part of its redesign. But the reporting of the company remains to be largely oriented on input and direct output levels.