This paper presents the analysis of the performance of orthogonal space-time block coding (OSTBC) over fading channels with impulsive noise. We adopt anε -mixture Gaussian noise model for the noise distribution. Based on an equivalent scalar additive mixture noise channel with a channel gain proportional to the Frobenius norm of the matrix channel for OSTBC, we derive the closed-form expressions for the average symbol error rate (SER) of OSTBC over Rayleigh, Rician and Nakagami-m flat fading channels under the impulsive model. Furthermore, we evaluate the SER performance of the OSTBC for different code matrices with MPSK and MQAM modulations. Simulation results show fine agreement with the analyses.