This paper presents a hybrid method to determine the optimal locations and sizes of DG units in distribution networks using Fuzzy and one rank cuckoo search Algorithm (ORCS). The main objective functions are to reduce total power losses and to improve voltage profiles of power distribution networks. As major power losses are occurring on distribution networks, Keen interest is evinced to reduce them. Due to the increasing interest on renewable sources in recent times, the studies on integration of distributed generation to the power grid have rapidly increased. The Distributed Generation (DG) sources are added to the networks mainly to reduce the power losses by supplying a net amount of power. In order to minimize the line losses of power systems, it is equally important to define the size and location of local generation. In this paper fuzzy approach is used to find the optimal DG locations and one rank cuckoo search algorithm is used for optimal sizes of the DG units. The proposed method is tested on IEEE 15-bus, 33-bus and 69-bus test systems and the results are presented.