In this paper, a microwave imaging technique for reconstructing the shape of two-dimensional perfectly conducting scatterers by means of the particle swarm optimization algorithm is proposed. The reconstruction is based on scattered field simulated measurements derived by transverse magnetic illuminations. Two different implementations of the particle swarm optimization algorithm, namely the synchronous and the asynchronous one, are considered. Furthermore, the robustness of the algorithm with respect to different initial particle populations is investigated. Finally, the performance of the technique in the case of noisy scattered field data is examined.