Mechanical fastening of fiber-reinforced polymer (FRP) composites presents a critical design challenge, as the drilling of fastener holes introduces fiber discontinuities and promotes delamination damage, which is further exacerbated by contact with bolts during service. This paper investigates the mechanical performance and damage mechanisms of conventional composite bolted joints (CBJ) and hybrid fastening systems (HFS) constructed with plain-woven glass fiber /epoxy composite substrates. The basic configuration of HFS consists of a bolt with a channel through its shank for the injection of an adhesive to fill the bolt-hole clearance and the delamination caused during hole-drilling. Upon curing, the bolt/adhesive-insert acts as a monolithic structural system, enhancing the resulting mechanical performance. Quasi-static tensile-shear loading tests were conducted at room temperature at a rate of 10mm/min for both CBJ and HFS. Results show that the HFS effectively eliminates bolt-adherend slip, significantly delays the onset of delamination, and increases the peak strength. It was shown that: i) if bolt-adherend slip is critical, the HFS performs 4-7 times better than the conventional CBJ, ii) If onset of delamination is considered, HFS is 2-3 times better than the CBJ, and iii) If joint stiffness is a priority, a significant improvement is observed in all configurations of HFS. Collectively, these results provide strong experimental evidence for enhancing the mechanical reliability of composite joints through hybrid fastening strategies.