As key venues for interaction and cooperation, international river basin organizations (IRBOs) are significant contributors to hydrodiplomacy in transboundary river basins. As part of their efforts to support hydrodiplomacy, IRBOs engage in the production and use of science. The manner in which that science is produced, and how it contributes to hydrodiplomacy, is not well understood. This paper examines the production and use of science by three IRBOs: the (US – Canada) International Joint Commission, the International Commission for the Protection of the Danube River, and the Mekong River Commission. We find the science produced by the IRBOs to support hydrodiplomacy extends beyond measuring and monitoring to include more advanced and analytical forms of science. In producing science, we observe that the IRBOs balance considerations of capacity, ownership, and how the politics of the basin will influence the production and use of the science. Given the challenge of balancing across these considerations, future research is needed to determine what mechanisms and processes for producing science can best facilitate its use in hydrodiplomacy.