To reduce the fuel consumption and enhance the flight performance of satellites, it is desirable to employ structural components of low weight, high strength, and high stiffness. Therefore, most primary and secondary structures of satellites are built using sandwich panels. Fasteners, which constitute secondary structures, are normally used as joining parts in different types of inserts such as partially potted, fully potted, and through-thickness inserts. Finite element analysis (FEA) is valuable for predicting the behavior of such primary and secondary structures. However, to obtain more realistic results from such analysis, it is necessary to define suitable fastener stiffness values. To this end, in this study, a method for calculating the fastener stiffness of a fully potted insert for sandwich panels using a finite element model is exemplarily developed and experimentally validated. In addition, a shell modeling is established for various connection types to further save time and reduce the computational cost of the finite element model. Finally, the effects of the fastener stiffness on the numerical analysis results for satellite structural system are evaluated. The two-dimensional (2D) structure modeling method used in this study was found to be as fully sufficient as three-dimensional modeling. In addition to saving time and cost, 2D FEA numerical modeling and prediction could reduce elaborate test costs.