The construction sector, an important segment of the economy, is also responsible for considerable environmental impacts, from the extraction of raw materials to the generation of substantial quantities of construction and demolition waste (C&DW). Consequently, initiatives that are focused on reducing waste generation and promoting its reuse are in accordance with the objectives of sustainable development. A large proportion of C&DW is comprised of an inert fraction, which exhibits properties analogous to natural aggregates. This study proposes a methodology for characterizing C&DW, with the aim of utilizing it as a filling material in gabion retaining structures. The heterogeneity of C&DW has demanded the adaptation of procedures from those used for the physical and mechanical characterization of natural aggregates. The text presents and discusses preliminary results of the application of the methodology, including physical characterization, strength and durability index tests, and compression tests on gabion modules, conducted with C&DW processed at a C&DW recycling plant in Belo Horizonte, Brazil. The C&DW was divided into three groups: gray fraction (cementitious materials and rocks), red fraction (ceramic materials), and the mixed fraction. The outcomes of the study suggest that the gray fraction has considerable potential for application as a filling material in gabion retaining structures.