Suction caisson foundation systems have been successfully used in the past two decades in numerous occasions on a variety of offshore structures in a wide range of environments. The pull-out capacity of suction caissons remains a critical issue in their applications, and reliable methods of predicting the capacity are required in order to produce effective designs. In the current study a numerical approach has been chosen to investigate the behavior of suction caissons under pull-out loads. The model has first been calibrated against available experimental data and also been verified against other test data. The verified model has then been used to study the influence of a number of parameters on the pull-out behavior of suction caissons. Variations in the soil type, soil cohesion, internal friction angle, dilatancy angle, Poisson’s ratio and the aspect ratio of the caisson have been studied. Soil nonlinearities, soil/caisson interactions, drainage conditions and suction effects have also been taken into consideration. Simple approximations have been put forward to express the effects from above mentioned different parameters on the pull-out capacity. These approximations have also been compared with some analytical and simplified relationships proposed by other researchers.