The upgrading of bio-oil with the existing distillation technologies is mainly hindered by polymerisation due to the reactive nature of bio-oil when it is heated up during distillation. We propose that the distillation of bio-oil at high pressure can significantly reduce the extent of polymerisation. This study aims to investigate the roles of process parameters, especially pressure, in the high-pressure reactive distillation of bio-oil produced from the pyrolysis of mallee woody biomass. The bio-oil distillation fraction yields and properties were evaluated to demonstrate the advantages of the distillation at elevated pressures over distillation at atmospheric pressure. Our results indicate that high-pressure distillation can achieve high distillate yields with reduced polymerisation because high pressure can retain water and other light components in the liquid phase to reduce the extent of polymerisation. Besides reducing the polymerisation, high pressure could also intensify the separation during the flash separation step. The distillate yield was around 90% when the distillation was carried out at 200 °C at a pressure higher than 20 barg. •High-pressure distillation of bio-oil can reduce the polymerisation extent.•High-pressure distillation of bio-oil can achieve high distillate yields.•High pressure can retain water and other light components in the liquid phase.•Distillate yield is ~90% when distilling bio-oil at 200 °C and pressure ≥20 barg.