Provided are a dielectric material, a device including the dielectric material, and a method of preparing the dielectric material, in which the dielectric material may include: a layered perovskite compound, wherein the layered perovskite compound may include at least one selected from a Dion-Jacobson phase, an Aurivillius phase, and a Ruddlesden-Popper phase, a temperature coefficient of capacitance (TCC) of a capacitance at 200° C. with respect to a capacitance at 40° C. may be in a range of about −15 percent (%) to about 15%, and a permittivity of the dielectric material may be 200 or greater in a range of about 1 kilohertz (kHz) to about 1 megahertz (MHz).