This article provides an update on key recent developments in investor-state arbitration concerning various aspects of third-party funding. These include the obligation to disclose third-party funding and the scope of such disclosure obligations; the implications of third-party funding for the allocation of costs and security for costs applications; the funder’s influence on the funded party; and confidentiality and privilege issues.The article begins with a brief overview of related developments in national legislation and case law, which have been influential in driving trends in investor-state arbitration, but which also are important to keep in mind when it comes to enforcing an arbitral award.