Work-related incidents can impact gravely on those directly involved with them and their effects can ripple throughout society. Work health and safety (WHS) incident investigations aim to determine causes and implement controls. Systems thinking is a contemporary philosophy for accident causation, but has yet to be widely adopted by regulatory incident investigators. This study examined WHS inspector perceptions and understanding of systems thinking to identify the factors influencing these within the regulatory context. A qualitative orientation including the scenario invention task technique was used to elicit rich insights from regulatory inspectors (N = 22) in one-to-one interviews. Thematic networks analysis revealed three organising themes: (1) Systems thinking = thinking in Safety Management Systems, reflecting a misattribution of systems thinking to procedures, processes and policies; (2) the WHS regulatory inspector role is multifaceted and has an inherent complexity, reflecting the challenges and dualities in the role; and (3) the WHS regulatory context narrows even as it focuses incident investigation, reflecting the process-orientation and congruence of a lower system level focus with legislation. Despite an unfamiliarity with systems thinking, some aspects were represented across scenarios (multiplicity, inter-relationships, changes over time), others were minimal (non-linearity), and some absent (e.g., emergence). The global theme was tunnel vision, conceptualised as an inability, limited capacity, or reluctance to consider alternatives to the preferred line of thought induced by the regulatory context. This narrowed the decision space towards immediate causes of breaches and away from broader systems influences. Implications of the findings and future research directions are given.