What is the relationship between adverse working conditions and employees' organizational citizenship behaviour (OCB) in small and medium-sized enterprises (SMEs) operating under a severe economic crisis? To address this question, a survey of 312 front-line workers was undertaken in 62Greek SMEs − an instrumental setting where the current deterioration of working conditions is acute. Our contribution is twofold. First, we develop and test a scale for measuring adverse working conditions. Second, we decipher the extent to which such conditions relate to organizational and individual aspects of OCB, considering job satisfaction's mediating role. Through this research we extend the OCB literature within the context of SMEs operating under severe economic crisis and highlight the implications for managing human resources in SMEs, a sector conspicuous for its socio-economic significance and its vulnerability during economic downturns.