Purpose: The present article aims to analyse the relationship between the stress experienced by the employees of knowledge-based organizations and the desire to demonstrate prosocial organizational behaviours, which are fundamental for knowledge sharing, as well as to examine the mediating effect of the organizational climate on that relationship. Design/methodology/approach: An empirical, quantitative study was conducted among a sizable sample of knowledge workers (N=677) employed in over 150 knowledge-based organizations operating in Poland, which is the country with a strong knowledge-based economy. Two psychometric questionnaires and one author's own questionnaire were used. To verify the hypotheses, multiple linear regression and mediation with bootstrapping analyses were conducted. Findings: The results of statistical analyses demonstrated that there is a negative correlation between the level of occupational stress and engagement in prosocial behaviours. Also, this relationship is fully mediated by an assessment of the organizational climate, especially the quality of communication, relations with colleagues and work organization. Practical implications: The research results provide pragmatic guidelines for management practices in knowledge-based organizations, ones that may contribute to increasing prosocial organizational behaviours as a basis for information and knowledge exchange in the knowledge-based economy. It is particularly important to ensure the reduction of stress level; it is also vital to improve communication and relations between personnel and to make the organization and control of work more flexible. Originality/value: This research significantly expands the literature on prosocial organizational behaviours, organizational climate and occupational stress, which is of a great importance in the knowledge-based economy. Moreover, the results show that, despite other research, there are organizational factors more significant than management style and approach, which are crucial for performing prosocial organizational behaviours.