This study presents a new MOMICA (Multi-Objective Modified Imperialist Competitive Algorithm) for the multi-objective OPF (optimal power flow) problem. The OPF problem can be solved for minimum generation cost which satisfies the power balance equations and system constraints. However, cost based OPF problem solutions usually result in unattractive system emission, losses and voltage profiles. In this paper, the fuel cost, emission, voltage deviation and active power losses impacts are considered as the objective functions for the proposed multi-objective OPF problem. The obtained final optimal solution using MOMICA is compared with that obtained using multi-objective algorithm in the literature. The performance of multi-objective algorithms is studied and evaluated on the standard IEEE 30-bus and IEEE 57-bus power systems. The proposed MOMICA method provides better results compared with the other algorithm as demonstrated by simulation results. (C) 2014 Elsevier Ltd. All rights reserved.