Abstract <p>A high-performance thin-layer chromatography method was developed for the simultaneous quantitative determination of diclofenac sodium and benzyl alcohol and employed for the assay of these analytes in pharmaceutical injection solutions. The method used a silica gel 60 F254 plate and a mixture of <i>n</i>‑hexane–chloroform–acetone–acetic acid (60 : 60 : 35 : 0.75, v/v/v/v) as the mobile phase for chromatographic separation of the analytes. The samples were applied on the thin-layer plate as 4-mm-wide bands with a band-to-band distance of 9 mm; the distance from the bands to the bottom of the plate was 1 cm, and the development distance was 85 mm. The applied sample volume was 6.0 μL. After plate development, the chromatograms were scanned at 210 nm to detect analytes and to calculate their peak areas. The method was validated according to the guidelines of the International Council for Harmonization and Association of Official Analytical Collaboration International in terms of system suitability, specificity, linearity, accuracy, precision, and robustness. The validation results confirmed that the method was suitable and reliable for the intended purpose and was applied for the quality control of commercial products.</p>