In this work, dense CdCu₃(Al${}_{1∕2}$Ta${}_{1∕2}{)}_x$Ti${}_{4?x}$O${}_{12}$ ceramics were prepared by a conventional solid phase method. The effect of Al${}^{3+}$/Ta${}^{5+}$ dopants on the dielectric properties of CdCu₃Ti₄O${}_{12}$ ceramics was systematically investigated. Upon Al${}^{3+}$/Ta${}^{5+}$ co-doping, the dielectric properties of CdCu₃(Al${}_{1∕2}$Ta${}_{1∕2}{)}_x$Ti${}_{4?x}$O${}_{12}$ were significantly enhanced. Particularly, the CdCu₃(Al${}_{1∕2}$Ta${}_{1∕2}{)}_{0.05}$Ti${}_{3.95}$O${}_{12}$ material displays a decent dielectric property, where dielectric constants (${\epsilon }_{\text{r}}～27181$), loss tangent (tan $\delta ～0.069$) at a test frequency of 1$$kHz are able to satisfy the application temperature requirement of the Y6R capacitor. Surprisingly, the refined grains resulting from Al${}^{3+}$/Ta${}^{5+}$ co-doping lead to heightened resistance at grain boundaries, which is closely associated with enhanced dielectric properties. Meanwhile, the giant dielectric property of the materials can be attributed to the effect of the internal barrier layer capacitance. The obtained results are expected to provide a new idea for obtaining high dielectric constant and low loss tangent in CdCTO-based materials and promote the practical application of such materials.