The electrical resistivity and magnetoresistance (MR) of single-crystal antiferromagnetic GdRh1.07Sn4.21 have been studied from 4.2 to 25K and in a magnetic field up to 30 kOe. Below TN the resistivity can be attributed to electron-spin-wave scattering. A positive MR at temperatures below TN is believed to arise from the field-induced enhancement of the spin fluctuations. The field dependence of the MR is quadratic at lower fields and it has an inverse temperature dependence below TN.