A new variant of harmony search algorithm called self-adaptive differential harmony search (SADHS) algorithm is proposed in this paper to solve the optimal power flow (OPF) problem with emission minimization. The primary objective of OPF with emission minimization is to determine the optimal generation cost at the same time reducing the emission level and satisfying the system constraints. In order to demonstrate the effectiveness of the proposed algorithm, it is applied on IEEE-30 bus system with and without valve point effects. The simulation results obtained by the proposed algorithm are compared with the results of DHS algorithm. The results obtained by the proposed algorithm are found to be better than DHS algorithm in terms of solution quality, speed of convergence and CPU time. © 2014 IEEE.