In flexible culvert design, it is generally assumed that the groundwater elevation is located at or below a structure's invert, meaning that porewater pressures in the backfill soil are negligible in the regions beside and above the structure. However, high groundwater conditions can develop during storm events causing an increase in porewater pressures, leading to reduced soil stiffness around the culvert due to lower effective stresses and modulus in the soil, all while the structure is expected to remain in service to vehicular traffic. Since flexible culverts rely on soil-structure interaction to resist vehicle loading, a reduction in the soil stiffness will decrease the load capacity of the structure. To investigate the effects of groundwater elevation on a culvert's live load response, a 0.9-m-diameter corrugated steel culvert was tested under simulated cyclic vehicle loading with three different soil conditions: dry soil, a groundwater level at the invert, and a groundwater level 0.6 m above the crown. The results indicate that high groundwater conditions led to increases in the peak bending moment and peak thrust responses of roughly 100% and 16%, respectively, when compared to the responses with low groundwater conditions. Additionally, the peak bending moment response displayed an increasing nonlinear trend to increases in live load while the thrust response increased almost linearly. Finally, in the first loading cycle with high groundwater conditions, the structure displayed a peak bending moment that was more than double the peak moment in the fourth loading cycle while the peak thrust decreased by 36% from the first to the fourth loading cycle. The results suggest that the effects of increased porewater pressures that develop during high groundwater conditions should be considered in the design of culverts in areas prone to large storm events.