In this paper, we investigate the outage behavior of a dual-hop N th-best decode-and-forward (DF) relay system with co-channel interference (CCI) at both the relays and the destination. The source-relay and relay-destination channels as well as the interferers' channels at both the relay and the destination nodes are assumed to follow Rayleigh distribution. Exact closed-form expressions for the outage probability for both independent non-identically distributed (i.n.d.) and independent identically distributed (i.i.d.) cases of interferers' channels are derived in this paper. Furthermore, the system behavior at high signal-to-noise ratio (SNR) values is studied via deriving an approximate expression for the asymptotic outage probability as well as the diversity order and the coding gain. The analytical results are supported and validated by Monte-Carlo simulations. Our findings suggest that the diversity order linearly increases with the number of relays and linearly decreases with the order of the relay. Also, the results show that the system is still able to achieve full diversity gain in the presence of finite number of interferers with finite powers.