Guided‐wave magneto‐optic Bragg cells atX‐band microwave frequencies using magnetostatic forward volume waves (MSFVWs) in bismuth‐doped yttrium iron garnet‐gadolinium gallium garnet (Bi‐doped YIG‐GGG) waveguides are reported for the first time. Performance figures that have been obtained at an optical wavelength of 1.303 &mgr;m include a center frequency tuning range of 3.7–12.0 GHz, a diffraction efficiency of 12% at the magnetostatic wave power of 56 mW, a linear dynamic range >40 dB, and a −3 dB magneto‐optic bandwidth of 150 MHz. These results represent a significant improvement over those obtained previously with the Bragg cells using pure YIG‐GGG waveguides. Maximum scan angle of 6° and 5.3° were also measured, respectively, by tuning the rf frequency ∼10.0 GHz at a fixed dc magnetic field of 3660 Oe and by varying the dc magnetic field ∼3660 Oe at a fixed rf frequency of 10.0 GHz. A frequency resolution of 30 MHz was measured with rf spectral analysis experiments carried out at 12 GHz. Finally, a Faraday rotation coefficient as large as −2313°/cm was measured for the Bi‐doped YIG‐GGG waveguides.