Numerical and experimental investigation on free and forced vibration of honeycomb core sandwich structure using the equivalent two-dimensional (2D) model is presented. Initially, a three-dimensional (3D) honeycomb core sandwich structure is converted to a 2D panel with equivalent properties obtained based on the honeycomb plate theory. Following this, the 2D panel is modelled using a layered structural shell element to obtain the vibration response using commercial element software. An experiment on harmonic analysis is carriedout on the honeycomb core sandwich structure. The results obtained based on numerical results of free- and forced-vibration responses match well with experimental results. Further, from the forced-vibration response ofboth experimental and numerical results, it is noticed that the second mode is not observed. This can be attributed to the excitation location corresponding to the nodal point of the second mode and this is verified with the mode shape obtained based on numerical and experimental analysis.