This paper aims to assess the finite element analysis in predicting the behavior of portal steel frames fabricated from cold formed steel (CFS) rectangular hollow sections. ABAQUS ® was used in the current research to discuss and validate the finite element models with experimental tests on portal frames and knee joints of portal frames. The influence of the nonlinear finite element solution methods, loading type controls, initial imperfections in CFS, residual stresses, mesh density, and different element types were studied. Also, the method of representing the initial imperfection were considered and found to have significant influence on the results. These considerations enabled performing an extensive parametric study. The parametric study consisted of 144 portal frames with various dimensions and RHS sizes. The ultimate load capacity as well as horizontal and vertical displacements that represent the nonlinear behavior of such steel frames were obtained. The failure modes due to material yielding, local buckling, plastic hinges formation as well as interaction of material yielding, and local buckling were also recorded.