Vibrational and microwave dielectric properties of xLa(Mg1/2Ti1/2)O3–(1−x)Ba(Mg1/3Nb2/3)O3 (x = 0.0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0) synthesized by the solid-state reaction technique are investigated. The Rietveld refinement of the X-ray diffraction (XRD) data confirms that Ba(Mg1/3Nb2/3)O3 (x = 0.0) adopts the 1:2-ordered structure with trigonal P-3m1 space group, whereas La(Mg1/2Ti1/2)O3 (x = 1) has monoclinic P21/n crystal structure. Both the materials have single phase crystal structure. For x = 0.1, the sample is found to have double phase. Further, with the increase in the value of x, the crystal structure becomes monoclinic P21/n. The vibrational properties of the materials are studied by the Raman spectroscopy and are correlated with the structural parameters. All the materials show high dielectric constant (εr > 35) at microwave range. The factors affecting the microwave dielectric properties are discussed based on the vibrational and structural data.