The microstructure development and the dielectric properties of La4Mg3W3O18 layered oxide were investigated. A strong anisotropic grain growth is revealed in ceramics sintered above 1400oC. The anisotropy of the grain reflects the anisotropic character of the crystal structure. Dielectric measurements yield a relative dielectric permittivity, ε, and a temperature coefficient of the dielectric permittivity, TC ε, to be 21 and 95 ppm K-1, respectively. The positive value of TC ε is assumed to be caused by the octahedral tilting by analogy with the behaviour of other complex ordered perovskites.