Under high amplitude vibrations, contact interfaces experience micro-vibro-impacts and frictional slips. These nonlinear mechanisms can introduce response nonlinearity and energy dissipation into the structures containing them. Beams are widely used in engineering structures and almost in every application they are subjected to boundary conditions. Boundary conditions may contain nonlinear contact interfaces. Therefore, modeling accurately the micro-vibro-impacts and frictional slips developing at the boundary condition of a beam is important in structural dynamics. Ignoring this may result in major discrepancies between experimental observations and theoretical calculations. In this paper identification of micro-vibro-impacts and frictional slips at boundary condition of a nonlinear beam is considered. The structure, being modeled as an EulerBernoulli beam, is analyzed using nonlinear normal modes. A reduced-order model governing the dynamic response of the beam near its first resonant point is resulted from the analysis. Identification of the nonlinear boundary condition parameters can be performed by means of the reduced order model and using experimental results.