It drains the south-western slopes of Mount Ruapehu, passes through Ohakune before discharging into the Whangaehu River to the south-west of Mangamahu.

[3] The 25 m (82 ft) high Mangawhero Falls is located in this top section of the river and is accessible via a short walk from Ohakune Mountain Road.

The river then turns to flow more southwards as it meanders through farming hill country passing the settlements of Oreore and Kakatahi.

The Ruakawa Falls were 15 m (49 ft) high but the clay wall that the river flowed over collapse in the 2010s reducing the height and grandeur of the waterfall.

The Whangaehu River continues southwards, eventually flowing into the Tasman Sea 12 km (7.5 mi) south east of Whanganui.