This study suggests a methodology for damage diagnosis in structures, which is based on a multivariate statistical procedure and uses the measured time domain structural vibration response. In this paper the methodology is developed for the purposes of delamination assessment in free vibrating composite laminate plates. It applies singular spectrum analysis to the measured strains in order to decompose and compress the information contained in these responses into a smaller number of independent variables. The method works on the principle of clusterization between healthy and delaminated plates with different delamination sizes and locations. The developed methodology is then applied and verified on numerically simulated and experimentally obtained results for composite laminate plates. The results demonstrate a good capability for clusterization between different delamination scenarios in composite laminate plates.