In this letter, we investigate the performance of antenna selection in amplify-and-forward (AF) MIMO two-way relay networks (TWRNs) where a simple unified system outage probability (OP) expression is obtained for Nakagami-m, Rician, and Weibull fading channels. To quantify the error performance of the TWRN, a closed-form expression of the overall symbol-error-rate (OSER) is derived for Nakagami-m fading. In addition, to gain further insights on the diversity order, asymptotic expressions of the system OP and OSER are obtained at high signal-to-noise ratio (SNR) regime. Moreover, the joint optimization problems of power allocation and relay location are considered to minimize the asymptotic system OP. Finally, the analytical findings are validated by the simulations.