This study reports a vacuum-assisted resin infusion method for achieving low-porosity carbon fibre/phenolic resin composites utilizing a low-viscosity (∼281 cp) phenolic resin enhanced by ZrO2 nanoparticles. The experimental results reveal that this method can yield composites with a low porosity of 8.6 ± 2.5 % and average pore size of 3.8 ± 1.73 μm, demonstrating mechanical properties that show great potential for high-temperature structural applications, such as rocket motor nozzles. Moreover, the resultant composites exhibit distinct advantages over composites produced using other out-of-autoclave and autoclave methods investigated in this study in terms of flexural strength and modulus after oxidation treatment. The vacuum infusion approach retains higher resin content in composites than the autoclave method, leading to increased residual modulus post-oxidation. Furthermore, incorporating ZrO2 nanoparticles in the phenolic matrix has significantly enhanced the residual mass, flexural strength, and flexural modulus of the composites following exposure to oxidation at 1200 °C.