This paper reports an investigation on the damage tolerance of adhesively bonded pultruded glass fiber–reinforced polymer (GFRP) joints under fatigue loading. Double-strap joints with and without bondline defects were subjected to constant amplitude fatigue loading. The study investigated the effects of the defect location, size, and number on the fatigue performance of the joints (i.e., failure mode, fatigue life). Results showed that the failure mode was a combination of delamination and adhesive fiber–reinforced polymer (FRP) interface debonding at the defect vicinities. The fatigue life of the joints was significantly reduced (up to 90%) when the defect was at the overlap end. A defect size larger than 10% of the total bonded area could yield a substantial reduction in fatigue life. Small defects (less than 10% of the total bonded area) could yield a reduction in fatigue life of up to 73% when their number exceeded four. The joint exhibited better damage tolerance under static than fatigue loading conditions.