A series of novel double perovskite Ca2GdNbO6: Eu3+ red-emitting phosphors have been synthesized by the conventional solid-state reaction route at various Eu3+ ion concentrations and sintering temperature. The crystal structure of phosphors was determined by an X-ray powder diffraction pattern, and the micromorphology was described by scanning electron microscope. The optical properties were analyzed through absorption spectra, photoluminescence spectra, decay curve, CIE chromaticity coordinate, and thermal stability. The synthesized Ca2GdNbO6: Eu3+ phosphors emit red light (614 nm) under 416 nm excitation. The emission intensity of the sample reaches the maximum when the Eu3+ ion concentration is of 0.5. The CIE chromaticity coordinate of Ca2GdNbO6: 0.5Eu3+ phosphor is (0.652, 0.347), located in the red region. The investigation results indicated that the Ca2GdNbO6: Eu3+ phosphors have potential application in white light-emitting diodes.