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The magnetic ordering of La 1/3 Sr 2/3 FeO 3 perovskite has been studied by neutron powder diffraction and 57 Fe Mössbauer spectroscopy down to 2 K. From symmetry analysis, a chiral helical model and a collinear model are proposed to describe the magnetic structure. Both are commensurate, with propagation vector k = (0,0,1) in R3c space group. In the former model, the magnetic moments of Fe adopt the magnetic space group P 3 2 21 and have helical and antiferromagnetic ordering propagating along the c axis. The model allows only a single Fe site, with a magnetic moment of 3.46(2)μ B at 2 K. In the latter model, the magnetic moments of iron ions adopt the magnetic space group C2/c or C2 /c and are aligned collinearly. The model allows the presence of two inequivalent Fe sites with magnetic moments of amplitude 3.26(3)μ B and 3.67(2)μ B , respectively. The neutron-diffraction pattern is equally well fitted by either model. The Mössbauer spectroscopy study suggests a single charge state Fe 3.66+ above the magnetic transition and a charge disproportionation into Fe (3.66−ζ )+ and Fe (3.66+2ζ )+ below the magnetic transition. The compatibility of the magnetic structure models with the Mössbauer spectroscopy results is discussed.