Thermally stimulated depolarization current (TSDC) measurements were carried out on BaNd1.76Bi0.24Ti5O14 microwave dielectric ceramics to investigate the relationship between depolarization effects and microwave loss. At microwave frequency, BaNd1.76Bi0.24Ti5O14 ceramics exhibit a high dielectric permittivity of 88, a Qf value of 8800 GHz, and a tau (f) value of +6.9 ppm/A degrees C. The temperature dependence of dielectric properties indicates the loss value of 0.0015 at 1 MHz above 350 A degrees C. Utilizing TSDC technique, the origins of different relaxations in BaNd1.76Bi0.24Ti5O14 ceramics were identified. Two TSDC relaxation peaks (peak A and peak B) are associated with trap charges and oxygen vacancies, respectively. Activation energies of the relaxation in the polarized specimens were also estimated from TSDC measurement results. Such defects significantly contribute to extrinsic loss.