Objectives: Fatigue in healthcare practitioners presents a risk to both patient safety and the safety and well-being of doctors and nurses. Management of fatigue-related risk is largely focused on hours of work limits, but these limits are fallible. The aim was to investigate the ways in which healthcare professionals manage fatigue-related risk beyond the hours. Methods: Qualitative data extracted from semi-structured interviews and focus groups with 189 healthcare practitioners from nursing and medical disciplines were subjected to thematic analysis to identify key themes of causes and consequences of fatigue, as well as strategies deployed within teams and by individuals. Results: The majority of fatigue risk management beyond hours of work limits occurs as informal processes that have evolved within teams. These processes can be characterised as non-technical skills and include error protection practices and fatigue-proofing strategies. Conclusions: The informal practices we identified represent a key layer of defence in a fatigue risk management system – that of recognising and responding to fatigue. A process to assess and formalise the error protection practices and fatigue-proofing strategies is required and any formal implementation should be supported by effective and fair incident reporting systems.