The relationship between corporate social responsibility (CSR) and marketing performance has been widely investigated recently, but mostly in relation to for-profit companies. This paper highlights the importance of this topic for nonprofit organizations (NPOs). Focusing on an Italian NPO operating in the performing arts and entertainment industry, two empirical studies (a quantitative survey and a qualitative exploratory enquiry) prove the strategic relevance of CSR in nonprofit contexts. The results demonstrate that CSR can be considered an additional dimension of the customer perception of service quality in NPOs and reveal that customer perception of the social responsibility of the studied NPO is strongly linked to its institutional mission and to the modalities through which it pursues that mission.