This paper determines analytically the effect of in-plane statically applied normal loads on nonlinear fundamental frequency of thin rectangular plate with edge constraints as simply supported – clamped – simply supported – clamped (SCSC). The weak-form variational principle was used to formulate the energy functional of the plate problems. Algebraic polynomial displacements were used as shape functions. Both linear and nonlinear buckling loads were numerically computed at various aspect ratios. The nonlinear fundamental frequencies were computed at various aspect ratios by considering the presence of in-plane applied normal loads and also by considering the absence of in-plane loads. Furthermore, the variations in the ratios of nonlinear to linear buckling loads; and nonlinear fundamental to natural nonlinear fundamental frequencies were determined at various aspect ratios. The numerical value of linear buckling load obtained for a square plate was compared with results from previous works found in literature, and there was satisfactory convergence with percentage error of 4.90. Conclusively from the analytical and numerical results obtained, in-plane statically applied normal loads affect the nonlinear fundamental frequency of thin rectangular SCSC plate.