In the framework of inverse scattering techniques, this paper presents the integration of a multi-resolution technique and the level-set method for qualitative microwave imaging. On the one hand, in order to effectively exploit the limited amount of information collectable from scattering measurements, the iterative multi-scaling approach (IMSA) is employed for enabling a detailed reconstruction only where needed without increasing the number of unknowns. On the other hand, the a priori information on the homogeneity of the unknown object is exploited by adopting a shape-based optimization and representing the support of the scatterer via a level-set function. Reliability and effectiveness of the proposed strategy are also assessed by processing both synthetic and experimental scattering data for simple and complex geometries.