The adsorption of isocyanurate silane on E-glass fibers has been investigated by scanning electron microscopy, diffuse reflectance Fourier transform infrared spectroscopy (DRIFT), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). The strength of the silane-glass interaction has been related to the extent of removal of the adsorbed species after washing with a range of solvents. The DRIFT and TGA methods both support the conclusion that tetrahydrofuran and acetone, used as washing liquids, adsorb onto the polymerized silane surface. Dichloromethane efficiently removes most of the physisorbed silane, while methanol is less efficient, but promotes a reorientation of the silane. The adsorption and the orientation of the silane is clearly dependent on the relative affinity for the solvent on the one hand and for the glass fiber surface on the other. The XPS N/O ratio and N Is signal defined both the silane removal and its reorientation on the fiber surface. The morphology of the treated fibers was studied by scanning electron microscopy.