PurposeThe purpose of this paper is to explore differences between non-family employees of family and non-family firms regarding the perceptions of organizational justice and levels of organizational commitment. Moreover, focusing on non-family employees of family firms, the study assesses the relation between the perceptions of organizational justice and levels of organizational commitment. Finally, the study seeks to understand which dimension of organizational commitment (i.e. affective, continuance, or normative) is more associated with the perceptions of organizational justice of non-family employees working in family firms.Design/methodology/approachThe empirical evidence is provided by a sample of 205 Portuguese employees, 98 non-family employees of family firms, and 107 non-family firms' employees, who responded to a questionnaire that included organizational justice and commitment measures. All firms included in the sample are small-sized privately owned companies.FindingsResults show that there are no differences between non-family employees of family and non-family firms regarding the perceptions of organizational justice. However, results reveal that there are significant differences regarding the levels of organizational commitment. Furthermore, it was found that, in family firms, non-family employees' perceptions of organizational justice are positively related to the levels of commitment, especially regarding the affective dimension.Originality/valueThis paper aims to contribute to the literature by addressing two classical organizational aspects, which are yet under-researched in the comparison between family and non-family firms, while pursuing to shed some light on the relationship between the perceptions of organizational justice and levels of organizational commitment of non-family employees working in family firms.