From there it runs northeast, through the Ruvubu National Park, up to the Tanzanian border. After a stretch along the border, the Ruvubu crosses properly into Tanzania, before joining the Nyabarongo River on the Tanzania–Rwanda border near Rusumo Falls, to form the Kagera River.
The path of the Ruvubu river runs northeast, traversing through Ruvubu National Park and reaching the Tanzanian border. After a section along the border, it enters Tanzania completely before merging with the Nyabarongo River at the Tanzania-Rwanda border near Rusumo Falls to form the Kagera River.