Dynamic mechanical analysis (DMA) has been used to investigate the effect of water and glass bead surface treatment on the properties of glass bead-epoxy composites. By treating or not treating the glass beads with a silane coupling agent, we fabricated composites with ostensibly good or poor interfacial adhesion. SEM images of fracture surfaces and water uptake data confirmed this picture. We used dynamic mechanical tests to measure the material properties of dry and wet specimens. Temperature sweep tests of atmosphere conditioned specimens indicated that the value of the loss tangent at the temperature of the alpha-relaxation peak was most sensitive to interfacial adhesion. For wet specimens, the magnitude of an additional relaxation process, denoted as the omega-relaxation, correlated strongly with water uptake and, indirectly, interfacial adhesion. Master curves constructed from frequency sweep tests also manifested differences among dry and wet specimens, but shift factor data suggested that these tests were more prone to complications due to water loss. Apparent activation energies of alpha- and beta-relaxation processes were statistically significant indicators of interfacial adhesion in dry and wet composites, respectively.