Steel-reinforced concrete (RC) slender columns are widely utilized in the construction of buildings and bridges, but their axial capacity is lower than that of shorter counterparts due to stability and buckling issues. However, steel reinforcement is susceptible to corrosion, which affects the durability and structural performance of RC columns over their service life. To overcome corrosion-related problems, non-corrodible glass fiber-reinforced polymer (GFRP) reinforcement has been employed in construction, proving efficient in resisting shear and flexural stresses. Nevertheless, current FRP design provisions in North America remain conservative regarding the contribution of FRP in columns, particularly in slender ones, due to the lack of experimental data. This study investigated the behavior of slender GFRP-RC circular columns under various axial load eccentricities. Three columns, with a slenderness ratio of 45, were constructed and tested under small, medium, and large eccentricities corresponding to eccentricity-to-diameter ratios of 8.5, 17, and 34%, respectively. Each column measured 4,000 mm in height and 355 mm in diameter with a reinforcement ratio of 1.21%. The results showed a material mode of failure in the form of gradual concrete crushing for all specimens. The specimen with small eccentricity exhibited sudden load drop after the peak load, whereas specimens with medium and high eccentricities experienced load stabilization associated with a significant increase in the secondary moments before the drop, indicating column instability. The axial load capacity decreased by 12 and 66% when the eccentricity-to-diameter ratio increased from 8.5 to 17% and from 8.5 to 34%, respectively.