In this study, we investigate the feasibility of co-processing biocrude in petroleum vacuum gas oil (VGO) hydroprocessing units. The biogenic component of the feed was biocrude produced by hydrothermal liquefaction of woody biomass, while VGO from oil sand bitumen was selected as the hydrocarbon feed. To improve its processability, the biocrude sample was distilled to remove high boiling components prior to testing. Systematic experiments were conducted in a continuous hydroprocessing pilot unit at co-processing ratios of up to 15 vol % biocrude and reaction temperatures of 350-380 degrees C, including baseline tests with pure VGO, to understand process impacts. The operating range where there was a minimal effect on hydrodesulfurization and hydrodenitrogenation activity levels over the baseline was at co-processing ratios below 10 vol % biocrude and temperatures of 370 degrees C and above. Monitoring of catalyst stability through check-back experiments with pure VGO revealed visible deactivation trends at co-processing ratios above 10 vol % biocrude. Radiocarbon analysis allowed the establishment of the fate of biogenic carbon added to the co-processing feed. This study suggests that VGO hydroprocessing units, as normally used at the front of fluid catalytic cracking and hydrocracking units in a refinery, could be a suitable cut-in point for biocrude within a carefully delimited operating window.