The interface between an epoxy adhesive and sheet molding compound (SMC) was studied by TEM. The interface width is less than 20 nm where it is sharp, and on the order of 40 nm where it is more diffuse. The interfacial area in the TEM sample is located first by the difference between adhesive and SMC microstructures. Where there are no microstructural features we can investigate further the location of the interface by using the Mg Kx peak from magnesia thickener in the polyester matrix of the SMC. Calcium carbonate crystals in the SMC extend to within less than 25 nm of the interface. Measurements of interface extent and roughness indicate that there is intimate contact and good mechanical bonding between the adhesive and SMC. The surface and interfacial energetics of this epoxy-SMC system were evaluated using sessile drop advancing contact angles. Good mechanical bonding observed by TEM is consistent with a small advancing contact angle of 20°the epoxy adhesive on the SMC at 121 °C which shows a good thermodynamic driving force for the intimate contact during the bonding process.