The present paper studies the nonlinear free flexural vibration of stiffened plates. The analysis is performed using a superparametric element. This element consists of an ACM plate-bending element along with in-plane displacements to represent the displacement field, and cubic serendipity shape function is used to define the geometry. The element can accommodate any arbitrary geometry, and the stiffeners either straight or curvilinear are modeled such that these can be placed anywhere on the plate. A number of numerical examples are presented to show its efficacy.