The stability of coastal dikes is critically challenged during the sudden drawdown of sea levels that precede a tsunami. This phenomenon, characterized by rapid changes in pore water pressures, significantly reduces the structural stability of the dike. The present study employs advanced numerical analysis to investigate the behavior of coastal dikes under such loading conditions. Utilizing finite element software, the research simulates the effects of sudden sea level drawdown on dike stability. The results indicate a marked reduction in stability during the drawdown phase, increasing the vulnerability of the structure to failure upon tsunami impact. Displacement of the coastal dike decreased significantly as the initial sea level was reduced. Negligible displacements were observed when the mean sea level was 20% of the dike height. However, as the depth of the sea level increased, the displacements caused by drawdown also increased. The dike remained stable only when the depth of the sea level in front of the structure was <20% of its height. When the sea level increased to 40% of the dike’s height, the factor of safety was reduced by 25.47%. The findings of this study underscore the importance of addressing these critical loading conditions in the design and maintenance of coastal defense systems. By incorporating lessons learned from past tsunamis, this research provides valuable insights for improving the resilience of coastal infrastructure against natural disasters, ultimately contributing to safer coastal communities.