The strategic management of human resources (GERH) aims to raise individual performance to achieve organizational strategies, with the line manager being considered, by scholars on the subject, as one of the most relevant agents in its implementation. Through multiple case studies carried out in three prominent organizations in their sectors of activity in Brazil, the present study seeks to identify the factors that facilitate or hinder the performance of the line manager's role in people management practices. Analyzing the literature on the subject, three categories of factors stand out: those related to the organization, those inherent to individuals, and HR professionals. From this, the result of the research demonstrates that the definition of the role of the line manager, the training of this agent, and the partnership with the HR professional are factors that significantly interfere with the performance of the line manager in the implementation of GERH. On the other hand, the decision-making autonomy of the GERH, the manager's style, and the availability of time for people management activities are factors that have the least influence. The research results also led to the construction of a theoretical model that seeks to understand how the process of implementing the role of the line manager in GERH practices occurs, as well as other factors related to the organization, the individual line manager, and the professional of that facilitate or hinder this process. The model's objective is to provide a reference for future studies and propose guidelines for organizations that intend to implement HRM with the strong participation of the line manager.