The river's headwaters are in Aoraki / Mount Cook National Park, where it is the outflow of the proglacial Tasman Lake.

It is also fed by the glacial waters of the tributary Murchison River, from Murchison Glacier, and the short Hooker River, an outflow of the proglacial lakes of the Hooker and Mueller glaciers.

The Tasman River flows south for 25 kilometres (16 mi) through the wide flat-bottomed Tasman Valley in the Southern Alps and into the northern end of the glacial Lake Pukaki, this forming part of the ultimate headwaters of the Waitaki hydroelectric scheme.

In 2019, a report by the Department of Conservation was released giving the results of a pilot study on the invertebrate biodiversity present in the Tasman River flood plain.

[4] This article about a river in Canterbury, New Zealand is a stub.