A cell-based smoothed discrete shear gap method (CS-DSG3) using triangular elements was recently proposed for static and free vibration analyses of Mindlin plates. In this paper, the CS-DSG3 is extended for free vibration analysis of cracked Mindlin plates by integrating the original CS-DSG3 with discontinuous and crack-tip singular enriched functions of the extended finite element method (XFEM) to give a so-called extended cell-based smoothed discrete shear gap method (XCS-DSG3). Three numerical examples are considered to illustrate the reliability and accuracy of the XCS-DSG3 for the free vibration analysis of cracked Mindlin plates.