An interlaboratory study (ILS) was conducted to determine the utility and precision of a test method for measuring fiber/matrix adhesion of carbon fiber-reinforced polymer matrix composites. The test method is based on voltage contrast X-ray photoelectron spectroscopy (VCXPS). The technique provides a quantitative measure of the relative amount of exposed fiber and exposed matrix at the fracture surface of a failed composite specimen. Eleven laboratories participated in two rounds of interlaboratory testing. The first round or pilot run was conducted to familiarize laboratories with the technique. Each laboratory collected data on one of eight material variants to compare with data from the host laboratory. In the second round each laboratory analyzed different coupons from the same composite laminate. Repeatability and reproducibility statistics were calculated and demonstrated that the method has interlaboratory utility. Precision statistics were influenced by the heterogeneity of samples generated from a single-carbon fiber-reinforced polymer matrix composite laminate.