Objectives: The study has aimed to identify the relations between the supplementary person–organization fit (P–O fit) and the perceived stress among managerial staff, with special regard to the mediating role of the effort–reward balance. Material and Methods: The study sample consisted of 715 middle-level managers, aged 25–64 years old, employed in large companies. To measure the selected variables, the authors used the Questionnaire of Effort–Reward Imbalance (ERI), Perceived Stress Scale – 10 (PSS-10), and Person–Organization Fit Questionnaire. Results: The regression analysis revealed that the perceived effort–reward imbalance partially mediated the negative relationship between the supplementary person–organization fit and stress. Conclusions: The results suggest that even when the characteristics of the manager and organization are highly congruent, the managers will experience stress if their work involves heavy effort or when this effort is not compensated properly. Int J Occup Med Environ Health 2017;30(2):305–312