Based on a longitudinal eight-year study (2006–2014) in a large Italian food co-operative, this paper analyses whether and how the development and the use of sustainability control systems have been able to promote the integration of sustainability within organisational strategy. The co-operative has implemented three main instruments (sustainability report, sustainability annual plan and participatory social plan), which have been able to promote sustainability integration by inducing technical integration and reinforcing the cognitive enablers. However, strong cognitive (and organisational) barriers have gradually stifled the cognitive enablers and have not enabled sustainability to be fully integrated into the organisational strategy. As such, the integration process was marginalised, also due to the negative economic performance of the co-operative. The paper shows that sustainability integration remains a fragile concept even in a co-operative, despite the similarities between co-operative values and the principles of corporate social responsibility. Theoretically, the paper offers empirical evidences concerning management control literature for sustainability.