Particle swarm optimization is developed to estimate the model parameters of a 2.5-D sedimentary basin. PSO have been implemented on synthetic data and two field data. An observation has been made that PSO is affected by some levels of noise, but estimated depths are close to the true depths. The PSO results are well correlated with borehole samples and provide more geological viability than Marquardt results. Despite its long computation time, it is very simple to implement.