The available provisions for the seismic design of fiber-reinforced polymer (FRP)-reinforced concrete (RC) columns were fundamentally derived from design models created for steel-RC ones due to the limited research data on the former. This, in turn, may justify the conservativeness of such provisions, particularly those concerning the design of confinement reinforcement for columns with different aspect ratios. This study investigates the effect of the aspect ratio and axial load level on the seismic response of columns reinforced with glass FRP (GFRP) by testing six full-scale GFRP-RC circular columns under earthquake-simulated loading. The experimental results revealed that, unlike steel-RC columns, changing the aspect ratio insignificantly influenced the hysteretic response of GFRP-RC columns, indicating that the available code provisions for confinement reinforcement design are overly strict. Furthermore, recommendations are proposed for the seismic design of confinement reinforcement in GFRP-RC columns.