Neutron diffraction measurements made on a HoAg powder sample exhibit superlattice reflections and confirm previous susceptibility data that antiferromagnetism develops below a Neel temperature of 33 ± 1° K . In the unannealed condition, the basic antiferromagnetic +−+− layer structure predominates in a tetragonal magnetic cell having adjacent (110) ferromagnetic planes with oppositely directed moments as in TbAg and DyAg . In the annealed state the magnetic reflections consist solely of first‐order satellite peaks of the basic magnetic reflections observed in the unannealed sample. One model for the magnetic ordering is a sinusoidally modulated transverse spin wave propagating in the tetragonal 〈100〉 direction with the moments polarized in the c axis direction. The modulation wavelength of 6.6 ± 0.3 unit magnetic cells or 48 ± 2 Å is incommensurate with the unit cell and does not vary with temperature. The maximum ordered moment at the Ho atom sites is 8.0 ± 0.2 μ B . The development of anti‐ferromagnetic ordering with temperature conforms to an approximate Brillouin behavior with J =2 .