This article aimed to investigate the mechanical performance of 3D integrated knitted spacer composites with a tubular shape, in term of internal hydrostatic and external static pressures (ESP). All the tubular-knitted fabrics were produced on a modern flat knitting machine using untwisted glass and HT-nylon yarns. Then, the epoxy resin was transferred through the whole fabric structure via vacuum infusion molding process. Produced tubular composites were subjected to internal hydrostatic and ESP. Accordingly, force-displacement curves were obtained and experimental results were discussed. The results revealed that the tubular composite samples containing non-knitting yarns show 27.33 and 37.50% improvement in internal hydrostatic and ESP, respectively, compared with the plain knitted fabric reinforced composite. Also, the finding demonstrated that mechanical performance of the tubular-knitted spacer composites is highly affected by aspect ratio and the number of connecting layers. Knitted spacer reinforced composite containing 5 and 10 connecting layers can improve the resistance against internal hydrostatic pressure 35.08 and 51.29%, respectively, compared with the plain knitted reinforced composites. In this case, 84.20 and 89.86% improvement can be achieved in term of the resistance against ESP.