Purpose - The purpose of this paper is to investigate whether perceptions of distributive, procedural and interactional justice can explain the frequently reported low organizational commitment of managers in corporate mergers. Specifically, it aims to examine whether each of the justice dimensions is significantly and uniquely related to affective commitment, which of the justice dimensions has the strongest relationship with the criterion, and whether instrumental evaluations or trust might function as a mediator. Design/methodology/approach - A total of 128 managers from 37 companies completed a questionnaire. They had been involved in domestic or European mergers or acquisitions, which varied in the application of fairness rules. Findings - Although each fairness dimension correlated positively with affective commitment, only interactional justice showed a unique relationship with it. Results indicate that both instrumental evaluations and trust can function as a mediator. Research limitations/implications - Because of the cross-sectional design, conclusions about the causal order of the variables cannot be drawn. Practical implications - The authors recommend that top managers should pay extra attention to timely, candid and specific internal communication with thorough and reasonable explanation of decisions, as well as the respectful treatment of managers. Moreover, the results indicate that managers reacted positively to fairness because it conveys positive relational signals, and because one can gain personal advantages through fair outcomes and processes. Originality/value - The organizational justice approach has not yet been applied, to the authors' knowledge, in quantitative field studies of mergers. Furthermore, this paper offers a contribution to the literature on fairness heuristic theory.