We report the results from magnetization and magneto-resistance measurements on polycrystalline Sr 2 Fe 1– x Cr x MoO 6 . A decrease in the saturation moment per f.u. is observed, which we attribute to site dilution for x⩽0.4 and anti-site disorder for x⩾0.6 along with a reduced Cr 3+ saturation moment when compared with Fe 3+ . The magneto-resistance also decreases with increasing Cr substitution. This may be due to increased disorder leading to an increase in spin-scattering near the spin-tunnelling grain boundaries for x⩽0.4. There is no evidence for spin-tunnelling for x⩾0.6 and the magneto-resistance can be attributed to a reduction in intra-grain spin-scattering with increasing magnetic field.