The crystal structure of (Sm0.6Y0.4)2Zr2O7 ceramic has been investigated by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) coupled with selected area electron diffraction (SAED) and Raman spectroscopy. XRD result shows that (Sm0.6Y0.4)2Zr2O7 ceramic exhibits a single defect fluorite-type structure. However, HRTEM and SAED observation reveals that additional weak diffuse reflections belonging to the pyrochlore-type structure appear in the electron diffraction patterns expect for the characteristic reflections of the defect fluorite-type lattice, which suggests short-range ordering in the bulk defect fluorite lattice. Raman spectroscopy also confirms the short-range order phenomenon at the micro- or nano-scaled regions