Uniform single-crystal CdMoO4 nanooctahedra in the hemline regime of 30 nm have been synthesized via a reverse-microemulsion route at room temperature. The as-prepared products were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). Room-temperature photoluminescence (PL) measurement exhibited a blue emission peaking at 438 nm under the 360 nm excitation, which is mainly attributed to the existence of intrinsic distortions into the [MoO4] tetrahedron moiety in the lattices.