This study investigates seismic performance of existing liquid pentane storage tanks located in a tank farm in the Kocaeli region of Turkey, known for its high seismic activity. The tanks are constructed to slide freely on the reinforced concrete foundation. The evaluation of the tanks’ seismic performance is carried out using three-dimensional (3D) finite element methods with nonlinear time-history analysis. The developed finite element model for assessing the seismic performance of the existing tanks considers dynamic interactions between the tank and its foundation, as well as the potential for tank supports to uplift and slide over the foundation. The study identifies significant deficiencies in the seismic performance of the existing tanks, primarily attributed to the lack of tank foundation anchorage. The tanks are retrofitted to improve tanks seismic behavior by anchoring the tanks supports to the reinforced concrete foundation using four Hilti anchors with injectable epoxy and prefabricated steel split sleeves that require no field welding. The retrofitted tanks undergo seismic evaluation to validate the effectiveness of the retrofit strategy and its impact on the tanks’ seismic behavior.