The paper deals with topical issues of improving the regulation at the international level of the rules concerning the conduct of arbitrators in international commercial and investment arbitration. Two new documents are highlighted: the Code of Conduct for Arbitrators in the Settlement of International Investment Disputes, prepared by the working group of the United Nations Commission on International Trade Law (UNCITRAL), and the 2024 edition of the guidelines of the International Bar Association (IBA) regarding conflicts of interest in international arbitration. The Code of Conduct for Arbitrators is applied in the framework of International Investment Dispute (IID) proceedings, but may be applied in the framework of proceedings in any other dispute by agreement of the parties to the dispute. Along with the requirements for the independence and impartiality of arbitrators, the Code introduces restrictions on the simultaneous performance of several functions, as well as establishes obligations to exercise diligence, conduct proceedings in good faith and competently, not delegate their decision-making responsibilities, maintain the confidentiality of proceedings; the requirement for the reasonableness of arbitrators’ fees, as well as provisions governing the role of tribunal assistants. The IBA Guidelines on Conflicts of Interest in International Arbitration are the most popular source of «soft law» among the sets of rules of international origin governing the impartiality and independence of arbitrators. It is often used in arbitration and judicial proceedings in various legal systems when considering issues related to the assumption of the functions of arbitrators, their appointments and challenges. The novelties introduced into this Manual, taking into account the 10-year practice of applying the previous edition, expand the list of circumstances to be disclosed, clarify a number of statements.