Optimal power flow (OPF) is one of the known problems of the power systems. Many numerical and heuristic methods were used to solve this problem so far. As seen from these studies in literature, heuristic methods are more effective and faster than numerical methods. This case is to make more attractive and mandatory the using of heuristic methods in optimal power flow solution of high voltage direct current (HVDC) systems. In this study, the optimal power flow solution of alternating current direct current (AC-DC) power systems is firstly accomplished by using the artificial bee colony (ABC) algorithm that is one of the heuristic methods. The proposed method is tested on two different test systems. The obtained results are compared to that of genetic algorithm (GA) and a numerical method in literature. In this study, the real transformer representation is also used for the transformers in the power systems. (C) 2013 Elsevier Ltd. All rights reserved.