Despite evidence on greater line managers involvement in many HRM activities, the overall picture of their HRM role is still blurred especially in terms of their coverage and depth of involvement in HRM activities. For line managers to deliver their HRM role effectively, it must be clearly defined so they can enact the role according to the expectations of their role evaluators, who include the line managers supervisors, employees and HR specialists. The expectations of role evaluators are important because the assessment of line managers performance depends on what the role evaluators perceive as valuable. However, the expectations of the role evaluators change and this is a factor that contributes to variation in the HRM role of line managers. This paper presents the preliminary findings of a study conducted in Malaysian airports. A qualitative study through case study was conducted at three airports. Drawing on role theory concepts, interviews were conducted with senior managers and HR representatives at these airports to explore their perceptions of the HRM activities of line managers. Content analysis was employed to interpret the interviews data for themes related to role theory. Results indicate differences on the perceived HRM activities of line managers between airports as they differed in terms of airport category, size and operation. This finding has important implications in developing the line managers HRM role as the structural differentiation is likely to influence the expectations of role evaluators, which is crucial in achieving consensus between the intended and actual implementation of line managers. Key Words: Line Managers, HRM Role, Role Theory, Malaysia.