One of the key elements of a fair trial, which influences other aspects of judicial proceedings, is the right to translation or interpretation for defendants who do not speak or understand the language of the court or for persons with hearing and speech deficiencies as well. Pursuant to Article 14(3)(f) of the International Covenant on Civil and Political Rights (ICCPR) and Articles 200, 201, 367, and 368 of the Iran’s Code of Criminal Procedure, the provision of translator/interpreter services must be ensured at all stages of trial, irrespective of the proceedings’ outcome. The right to interpretation/translation indicates that language can pose a significant obstacle to administration of justice. Therefore, the question that arises is whether the denial of the accused’s right to translation/interpretation harms the fundamental guarantees of a fair criminal trial? Assuming an affirmative, it is necessary to investigate what effects of this right have on criminal proceedings and other procedural rights. The findings indicate that translation/interpretation plays an inherent role in the trial process for linguistically disadvantaged defendants, as it is intrinsically linked to all procedural principles of a fair trial and the accused’s right to defense. Failure to foresee and respect this right cannot be remedied by any practical means. The existence of such a right guarantees the rationality and coherence of the legal structure, and the lack thereof causes legal chaos and disorder.