One way that illegal, unreported, and unregulated (IUU) fish catch is laundered into the seafood market is through transshipments at-sea. This practice, which often occurs on the high seas (the areas of ocean beyond national jurisdiction), allows vessels fishing illegally to evade most monitoring and enforcement measures, offload their cargo, and resume fishing without returning to port. At the same time, transshipment at-sea can facilitate trafficking and exploitation of workers who are trapped and abused on fishing vessels. This study gives an overview of high seas transshipment as well as evaluates transshipment at-sea regulations across 17 Regional Fisheries Management Organizations (RFMOs), which are responsible for regulating fisheries on the high seas. Transshipment at-sea regulations have become increasingly strict in most RFMOs since the late 1990s. However, only five RFMOs have mandated a partial ban, and only a single RFMO, the South East Atlantic Fisheries Organization (SEAFO), has mandated a total ban on transshipment at-sea. A total ban on transshipment at-sea across all RFMOs would support the ability of oversight and enforcement agencies to detect and prevent IUU fishing and also likely reduce human trafficking and forced labor on the high seas.