Suction pressure created during suction bucket installation may disturb the surrounding soil and affect its properties. Soil heaving can also occur owing to upward seepage inside the bucket embedded in sand, which hinders soil penetration; however, this mechanism is not well understood. Centrifuge model tests were performed to investigate this soil behaviour and its effect on the installation. Suction pressure, seepage flow, and soil plug heave were monitored under various installation conditions. Bender element and cone penetration tests were also conducted to evaluate the effect of soil plug loosening indirectly. The results illustrate the effects of upward seepage on soil plug heave during suction bucket installation. This study highlights the changes in the soil properties inside the bucket owing to the suction installation. This is an important design consideration for bucket installation, which also affects the bearing capacity of the suction bucket foundation.