The Taseko has its origins at Taylor Pass in the heart of an alpine area known as the South Chilcotin. Taylor Pass connects with Slim Creek, a major tributary of Gun Creek, which feeds the Bridge River via Carpenter Lake. From its source, it flows north then northwest before entering the south end of Upper Taseko Lake next to the Lord River, one of its major tributaries. The Tchaikazan River, another large tributary, also joins the river via the Taseko Lakes, entering at the area that separates Upper and Lower Taseko Lake. At the outlet of the two Taseko Lakes the river issues onto the broad Chilcotin Plateau. From source to Upper Taseko Lake, the Taseko is about 30 kilometres in length. From Lower Taseko Lake to the Taseko's confluence with the Chilko River is about 85 kilometres. Including the 25 kilometre length of both Taseko Lakes, the total length of the Taseko River is around 140 kilometres.