The double perovskite oxide strontium gadolinium tantalate, Sr2GdTaO6 (SGT) is synthesized by solid-state reaction technique. The Rietveld refinement of the X-ray diffraction pattern of the sample shows monoclinic phase at room temperature. FTIR spectrum shows two primary phonon modes of the sample at around 373 cm(-1) and 562 cm(-1). The electronic structure of SGT has been investigated by Vienna ab-initio simulation package. The eigen frequencies of different phonon modes have been calculated and compared with the experimental data observed by Raman spectroscopy. Dielectric properties of the sample are investigated in a temperature range from 303 K to 673 K and in a frequency range of 42 Hz -1 MHz. The relaxation peaks are observed in the frequency dependent spectra for imaginary part of the dielectric constant. The modified Cole-Cole equation is used to describe the relaxation mechanism in SGT. The frequency dependent conductivity spectra follow the Jonscher power law. (C) 2013 Published by Elsevier B.V.