In this letter, a switch-and-stay combining (SSC) in two-way amplify-and-forward (AF) networks with two relays is proposed and analyzed. In particular, the closed-form expression of the outage probability for the proposed scheme over Rayleigh fading channels is derived. Asymptotic performance analysis for high signal-to-noise ratio (SNR) is also presented. It is shown that the SSC scheme is capable of realizing full diversity order, and even achieving the same outage performance as the best-relay selection (BRS), when reasonable switching thresholds are set. Simulations are provided to corroborate the theoretical analysis.