The role of agency and the dynamics of systems are critical to understanding how people are managed. Ironically, while this is well understood in practice (e.g. Buckingham & Coffman, 1999) such understanding has not made a sufficient impact in HRM research. This chapter explores the critical role and agency of front-line managers through a systems lens. In so doing we note the limitations of existing understanding which tends to treat gaps between intended and experienced HRM as something to be avoided and mitigated versus acknowledged and embraced. By contrast, the classic lens of systems theory provides a rich intellectual heritage which captures the dynamics of front-line manager agency as grounded by contextually oriented concepts including emergence, informality, self-organizing and entropy. The latter half of the chapter animates these principles in action using the example of the front-line manager role in performance management. The chapter concludes by highlighting how the dynamics of system theory can help advance understanding of front-line manager roles, including that which treats informal practice and deviance from established rules as a practical reality versus a detrimental fault-line in HRM implementation.