It was investigated whether there was a potentially significant improvement to scarf joint bonding that was achieved through the dispersion of carbon nanotubes (CNTs) along the interface of the composite joint. The study examined various factors that might affect CNT-reinforced joint interface strength. Each composite joint consisted of a vinyl-ester matrix base (DERAKANE 510-A) interlaced with a carbon fiber weave (TORAY T700CF). During the curing process, the research explored several variables concerning the CNT application. The testing included single-walled CNTs (SWCNT), and conventional and bamboo-structure multi-walled CNTs (MWCNT) with varying length, purity, and concentration levels along the surface area of the joint interface. This wide array of data demonstrated the effect of CNTs introduction at the joint interface, and provided the ideal type, size, purity level, and concentration level for composite scarf joint bond reinforcement using CNTs. Furthermore, a computational model was developed to predict the strength of the scarf joints. The predicted model agreed well with the experimental data.