To improve the interfacial adhesion between carbon fibers and an epoxy matrix, carbon fibers were modified by oxyfluorination at different temperature conditions. Surface analyses of the oxyfluorinated carbon fibers were performed using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and dynamic contact angle measurements. The interfacial shear strength (IFSS) of a single carbon fiber/epoxy matrix was studied by employing single-fiber pull-out tests to confirm the interfacial adhesion. The pull-out behavior of the fiber from the matrix was discussed based on the Greszczuk’s geometrical model. Functional groups such as C-F, C-O, and COOH were present on the carbon fiber surfaces after oxyfluorination. Moreover, the presence of functional groups increased the surface polarity of the fibers, resulting in an increase in the IFSS owing to the improvement of the interfacial adhesive strength between the carbon fibers and the epoxy matrix.