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Oxynitrides such as LaTa(O,N)₃ are attractive materials as photoelectrodes for photoelectrocatalytic solar water splitting. The potential anionic ordering in their perovskite-type structure has been shown to impact the materials’ properties. Given the importance attributed to it, the present study reports a detailed experimental analysis supported by simulations of the anionic ordering of La_1−<i>x</i>Y<i>_x</i>Ta(O,N)₃. The influence of O/N and yttrium content on the anionic order was assessed. Neutron diffraction analysis was performed on four different nominal compositions—LaTaON₂, LaTaO₂N, La_0.9Y_0.1TaON₂, and La_0.9Y_0.1TaO₂N—at 10 K and 300 K to study potential long-range ordering. Neutron pair distribution function (PDF) analysis was performed on all samples at 10 K and on non-Y-substituted samples at 300 K to evaluate short-range ordering. There was no evidence of long-range O/N order in any of the compounds. In contrast, at a short range (1.5 Å ≤ <i>r</i> < 6 Å), a <i>Pnma</i> (<i>a</i>⁻<i>b</i>⁺<i>a</i>⁻) tilting pattern and local <i>cis</i>-ordering of the anions were seen. The latter faded rapidly, leaving the <i>Pnma</i> tilting pattern in a 6 Å ≤ <i>r</i> ≤ 11 Å range. At higher distances, the PDF analysis agreed with the <i>Imma (a⁻b</i>⁰<i>a⁻)</i> O/N disordered long-range structure. As the O/N content changed, not much difference in behavior was observed. Yttrium substitution introduced some disorder in the structure; nonetheless, it showed marginal influence on octahedral tilting and anionic ordering.