A procedure has been developed to investigate the dynamic response of composite structures, with embedded multiple delaminations. A recently developed improved layerwise composite laminate theory is extended to model composite laminates of moderately large thickness with delamination. The theory accurately predicts interlaminar shear stresses while maintaining computationally efficiency. Natural frequencies and mode shapes are computed for cross-ply laminates with delaminations placed at different locations. Experiments are conducted to validate the developed theory. Numerical results indicate excellent correlation with analytical solutions and experimental results. Parametric studies are conducted to investigate the effect of delamination location, both through the thickness and in-plane, and number of delaminations on the dynamic response. A potential application of the developed procedure is in structural health monitoring where accurate predictions of dynamic response in the presence of delamination are important issues.