Background <p>We aimed to investigate diclofenac sodium’s ototoxic and neurotoxic effects, which have already been shown to have a cytotoxic effect on cholesteatoma.</p> Material and methods <p>The subjects were divided into three groups: negative control group (S), experimental group (DS group) in which diclofenac sodium (DS) was applied, and positive control group (G) in which gentamicin was applied to evaluate the ototoxic effect of DS. Ototoxicity was assessed using distortion product otoacoustic emission (DPOAE) and auditory brainstem response (ABR) measurements and by histopathological examination. In evaluating neurotoxicity on the facial nerve, the subjects were divided into a negative control group and a DS group. In terms of neurotoxicity, the subjects were evaluated functionally and histopathologically.</p> Results <p>There was no significant difference between the three groups on day 0 measurements in DPOAE and ABR tests. Although a notable difference was observed between the three groups in the measurements taken on day 3, no statistically significant difference was found between the DS group and the G group. A significant difference was found between the three groups when comparing day 28 measurements. In the histological analysis of ototoxicity, the degree of cytoplasmic vacuolization, cellular degeneration, and dilatation was found to be significantly higher in the G group than in the DS group. There was no significant difference between the two groups in the functional and histological analysis of neurotoxicity.</p> Conclusion <p>Although DS has no neurotoxicity on the facial nerve, it was found to have an ototoxic effect, contrary to the current scientific literature.</p>