The urgent challenge of climate change, driven by rising carbon emissions, necessitates innovative strategies for carbon capture and storage (CCS). This study examines the impact of hysteresis in relative permeability on CO ₂ entrapment efficiency within saline aquifers, known for their significant storage capabilities. An aquifer model was analyzed through numerical simulation by varying hysteresis values from 0.2 to 0.5 to evaluate their impact on CO ₂ plume behavior, retention during water-alternating-gas (WAG) injection, and plume morphology. The CO ₂ plume exhibits a funnel-shaped configuration at low hysteresis with a narrow, pointed base, indicating a concentrated upward migration trajectory. In contrast, a hysteresis value of 0.5 results in diminished gas movement toward the upper aquifer, transforming the plume into a more oval shape. Results from the land trapping model further support our findings, revealing an inverse relationship where increased hysteresis enhances residual CO ₂ entrapment, reflected in trapping coefficient values ranging from 0.5 to 4. This underscores the model's efficacy in verifying gas trapping efficiency and safety during sequestration. Moreover, increased water flow generates stronger forces, pushing CO ₂ into narrower pore spaces, where it becomes trapped. Our findings indicate that increased hysteresis enhances CO ₂ retention by limiting vertical migration and significantly influences plume geometry, promoting stable and predictable distribution patterns. At higher hysteresis values, CO ₂ migration is significantly restricted, resulting in near-complete immobilization of the injected gas. This research highlights hysteresis's critical role in refining injection methodologies and enhancing plume stability for long-term CO ₂ storage.