CdGa2X4 (X: S, Se) semiconductor compounds belong to a class of so-called AIIBIII 2XVI 4 orderedvacancy compounds (OVCs) characterized by rather strong anisotropy, nonlinear optical properties and birefringence, which make them suitable for many technological and optoelectronic applications such as solar cells, nonlinear optical devices, narrow-band optical filters, tunable filters and ultraviolet photodetectors. In spite of extensive investigations of optoelectronic properties of cadmium thiogallate and selenogallate, there are little ones [1] concerning their mechanical behavior. In this study the deformation peculiarities of CdGa2S4 and CdGa2Se4 subjected to point contact (indentation) were investigated. By applying a depth-sensing nanoindentation technique with Berkovich pyramidal diamond indenter, the hardness (H) and Young‟s modulus (E) were evaluated. The values of H and E show an increase with load decrease (Fig. 1) for both compounds that can be the result of the known indentation size effect. At the same time CdGa2Se4 demonstrates higher hardness and some lower Young‟s modulus comparatively with CdGa2S4. An additional influence on the drop of hardness with load increase can be induced by the enhanced fragility of materials. The cracking threshold for both CdGa2S4 and CdGa2Se4 is about 20 mN, this leading to the modification of load versus penetration depth dependences, which exhibit pronounced expulsion of the indenter from the material as a result of crack growth at the end of unloading (Fig. 2). The enhanced fragility of the materials in study is probably caused by the inner structure possessing a high concentration of vacancies that is known to impede the movement of dislocation and at the same time to give rise to the generation of cracks.