This paper analyzes the achievable secrecy transmission rates (STRs) of Alamouti space–time block coding (STBC) with the decision feedback (DF) detection in wiretap time-selective fading channels and studies how to optimally design the Wyner’s codebook to maximize it. Specifically, we derive the STR with both connection outage probability and secrecy outage probability for an arbitrary temporal correlation and find the optimal codeword rate and the secrecy rate to maximize it.