Strong evidence supports an early return to work after injury as a way to improve recovery. In Australia, General Practitioners (GPs) see about 96 of injured workers, making them the main gatekeepers to workers entitlements. Most people with compensable injuries in Australia are certified as unfit to work by their GP, with a minority of patients certified for modified work duties. The reasons for this apparent dissonance between evidence and practice remain unexplored. Little is known about the factors that influence GP sickness certification behaviour in Australia. The aim of this study is to describe the factors influencing Australian GPs certification practice through qualitative interviews with four key stakeholders.