GdAgSb(2) has been studied using (155)Gd Mössbauer spectroscopy and neutron powder diffraction at a wavelength of 2.3672(1) Å. Commensurate antiferromagnetic order develops below T(N) = 13.8(4) K with the 6.2(3) μ(B) Gd moments lying in the ab-plane of the tetragonal cell. The magnetic ordering is characterized by a [½ 0 0] propagation vector (i.e. the magnetic cell is doubled along one of the crystallographic basal plane axes) with the Gd moments oriented perpendicular to the doubled direction. These results are fully consistent with an earlier determination by x-ray resonant magnetic exchange scattering.