Opportunistic relay selection is an important approach to enhance physical layer secrecy of relaying networks, but that severely depends on the obtained CSIs. In this letter, we study the impact of limited CSI feedback on the secrecy performance of cooperative decode-and-forward (DF) relay networks with opportunistic relay selection. We first derive the exact closed-form expression for the secrecy outage probability (SOP), and the asymptotic expression for SOP in the high signal-to-noise ratio (SNR) region. Then, based on the derived expressions, we evaluate the impact of limited CSI feeback on secrecy outage probability and secrecy diversity order. Numerical results show that the secrecy diversity order is 2, regardless of the number of feedback bits. However, increasing the number of feedback bits can improve the secrecy outage performance.