The interfacial shear strength (IFSS) of a specific carbon fiber/epoxy composite (T650/Cycom 5320-1) was investigated to determine how changes in post cure temperature affects the fiber/matrix adhesion. The degree of cure of the Cycom resin cured with the same post cure temperatures was also determined using a DSC technique. The mechanical and viscoelastic properties of the samples made from Cycom 5320-1 resin were also measured and related to the degree of cure. It was shown that the mechanical and viscoelastic properties changed as the curing temperature, and hence the degree of cure, increased. The results of the micro-droplet tests showed the interfacial adhesion increased with increasing the post cure temperature. This was attributed to the higher degree of cure and change in mechanical and viscoelastic properties of the resin, as well as the residual stresses as the post cure temperature increased.