An enhanced particle swarm optimization algorithm (PSO) is presented in this paper to solve the optimal planning of multiple distributed generation sources (DG) in distribution networks. This problem can be divided into two sub-problems: The DG optimal size and location that would minimize the network real power losses. The proposed approach addresses the optimal size and location problems simultaneously by enhanced PSO algorithm that is capable of handling multiple DG planning in a single run. It treats the problem constraints differently by adopting a radial power flow algorithm to satisfy the equality constraints, i.e. power flows in distribution networks, while the inequality constraints are handled by making use of some of the PSO intrinsic features. To demonstrate its robustness and flexibility in accommodating different scenarios, the proposed algorithm was tested on the standard 69-bus power distribution system. Different test cases were considered to validate the proposed approach.