<p>Hoop tensile strength is the main index for evaluating mechanical properties of pipes used in fields such as pressure vessels and pipeline transport. Mechanical properties and failure mechanisms of glass fiber-reinforced polymer (GFRP) composite pipes with different thicknesses under hoop tensile loading were investigated. A finite element model capable of predicting hoop tensile strength and failure behaviors of GFRP pipes was developed. Results show that matrix tensile failure is the dominant failure mode. Pipes with thicknesses ranging from 2.4 to 8.0 mm were selected for finite element analysis. Results show that the hoop tensile strength of the pipes decreases by 24.7%. In addition, finite element analysis was used to investigate the effect of thickness on failure mechanisms of pipes. Results show that by increasing the thickness of pipes, matrix can exhibit three failure modes sequentially, which are complete matrix tensile failure, localized matrix tensile failure, and no matrix tensile failure. The presence of the latter two failure modes reduces the hoop tensile strength of pipes by 5.82% and 6.99%, respectively, which can exacerbate the decrease in hoop tensile strength of pipes. These findings provide a theoretical basis for accurately evaluating the effect of thickness on hoop mechanical properties and failure mechanisms of GFRP pipes.</p>