Herein, optical (e.g., UV–Vis reflectance spectra, infrared and Raman spectroscopy) and magnetization properties of the double‐perovskite compounds Ba2DySbO6(BDS) and Ba2GdSbO6(BGS) are reported. Optical bandgap is determined to be 4.524 eV for BDS and 4.465 eV for BGS using Kubelka–Munk function fit to the UV–Vis spectra. The lattice dynamical calculations on the force‐field model are undertaken for assigning the observed infrared and Raman modes. The dc susceptibility does not exhibit magnetic ordering down to 2 K for the two compounds. The dc magnetization atT = 2 K does not saturate for BDS even at a magnetic field of 11 T, but saturates at 5 T to a value of 7μB/Gd3+for BGS. A frequency‐dependent cusp in the ac susceptibility appears at 3.3 K, that is unlikely generic spin‐glass‐like freezing, and may be attributed to the short‐range correlations among Dy3+‐moments in BDS. Crystal‐field (CF) computations are performed to analyze the magnetic data for BDS. The obtained CF level scheme of Dy3+ions demonstrates the observed susceptibility and isothermal magnetization curves very well. The field‐dependence of the two lowest CF levels along different principal axes does not exhibit any level crossing, consistent with the lack of ordering in Ba2DySbO6.