Studies show that Human Resource Management (HRM) practices, the role of leadership, organizational citizenship behavior, and organizational virtues influence the greater involvement of professionals at work and, consequently, the organizational performance. However, there is a lack of investigations encompassing these four variables in the same research model. Thus, the main objective of this study was to identify the relationship between leadership, organizational virtues, HRM practices, and organizational citizenship behaviors in a sample of employees of Brazilian companies. A printed questionnaire was administered to a valid sample of 659 subjects, who participated voluntarily, from public and private organizations in a Brazilian State. A total of seven hypotheses were tested using confirmatory factor analysis to assess the fit of the measurement models of the four studied variables, in addition to path analysis, using structural equation modeling to specify and estimate the mediation models. All hypotheses were confirmed, attesting to the positive predictive associations between the variables. We also confirm the partial mediation of HRM practices in the relationship between leadership and citizenship and the total mediation in the relationship between virtues and citizenship. This research advances the efforts to test more complex and unexplored structural models in which HRM practices are mediating variables, fulfilling a gap in the literature, as well as providing investigations of antecedents and consequents of the variables adopted in the research. As practical implications, the findings constitute a diagnosis for managers to understand how these relationships happen, supporting decision-making towards an increasingly effective, strategic, and humanized HRM.