In this work we synthesized BaTaO₂N and SrTaO₂N using a two-step high-temperature solid-state reaction method and analysed the structural distortions, relative to the ideal cubic perovskite structure, according to group theory. From a complete distortion analysis/refinement using high-resolution neutron diffraction data in the temperature range 8 to 613 K, we identified tetragonal structures for BaTaO₂N [P4/mmm(No. 123)] and SrTaO₂N [I4/mcm(No. 140)]. In contrast to an anion-disordered cubic perovskite (Pm \overline{3}m No. 221) with Ta at the cell center, both systems show a site preference for oxygen anions in the two opposite corners (along thecaxis) of the Ta–O/N octahedra rather than the four square corners in theabplane (Γ₃⁺occupancy distortion), which induces a tetragonal elongation of the unit cell with thecaxis being longer than theaaxis. A further Ta–O/N octahedra displacement [R₅⁻(a,0,0), rotation about thecaxis] distortion was observed in SrTaO₂N. This distortion mode is accompanied by an increased unit-cell distortion that decreases as the temperature increases. Ultimately a second-order phase transition caused by the loss of theR₅⁻(a,0,0) mode was observed at 400–450 K.