The flexural motion of a rectangular sandwich panel with mass attachments is investigated both analytically and experimentally. Differential equations are derived that include the effects of rotatory inertia of the panel and masses, transverse‐shear deformation of the core, damping, and in‐plane loading. The influence of the concentrated masses on the natural frequency is first obtained and compared with experimental values. The dynamic response of a simply supported panel with mass attachments to a point sinusoidal excitation is then calculated and compared with experimental values. The effect of in‐plane loading on the natural frequencies and response to a point loading is considered. The variation of the natural frequencies due to the rotatorv inertia of the panel and mass attachments is discussed in detail. The results of a number of special cases are discussed and compared with experimental values.