Legal instruments within the multilateral system almost always become multilingual through translation. Given the legal force of the target texts that they prepare, translators take on the delicate responsibility of drafters of binding provisions in the target language in that context. This article focuses on multilateral treaties in order to illustrate the legal and situational factors framing that task at international organisations. Relevant provisions regarding the interpretation of multilingual treaties (within the Vienna Convention on the Law of Treaties) are analyzed as a starting point to address the scope of characteristic translation problems posed by ambiguity in original texts, as well as to identify the parameters that should be considered when dealing with such issues. Special emphasis is given to familiarisation with applicable rules of interpretation in international law and related judicial precedents at organisation level. The conclusion accordingly underlines the high degree of specialisation required for the translation of treaties, with a view to contributing to maximum text quality and concordance, and ultimately to legal certainty.