Over the recent years, much research has been conducted on using advanced composites such as carbon-fiber reinforced polymer (CFRP) to strengthen deteriorated metallic structures and aged bridges in particular under fatigue loading. However, the approved efficiency of CFRP is only considered in reducing stress intensity factor at the crack tip under mode I, while other modes (mode II shear, mode III torsion) may become critical when the cracks oriented. This paper presents an experimental program to evaluate the CFRP strengthening performance of oblique center-cracked steel plates subjected to mixed-mode (tension and shear) fatigue loading. The mixed mode conditions were stimulated by initiating different degrees of crack inclination with respect to the loading axis in steel plate specimens. This study aims to fill the knowledge gap of improved fatigue life of CFRP strengthened steel plates with inclined cracks.