It rises in Silt Lake about 85 km northwest of Pemberton and Whistler, and empties into the Harrison Lake.
The approximately 95 km long high valley ends in Lillooet Lake at the former Port Pemberton, drove on a place of the gold prospectors from 1858 Lillooet direction to go from there to get to the Fraser River ( Fraser Canyon Gold Rush). At the headwaters of the river in 1997 the Upper Lillooet Provincial Park, which has nearly 200 sq km area was created. The lower half of the upper course forms an agriculturally used area called Pemberton Valley, which is also known as " Spud Valley " ( " Knollental "). 12 km above Pemberton flows into the river in the Little Lillooet Lake. The Lillooet Lake itself, a 25 km long lake, is located between the mountains of Garibaldi Provincial Park in the west and the Lillooet Ranges to the east.
Along the river live several Amerindian groups that belong to the St'at'imc. The Xa'xtsa live in Port Douglas at the upper Harrison Lake, the skatin at Skookumchuck Hot Springs, at the Lillooet River, where the Samahquam live. The group at Mount Currie, was named according to their place of residence and Mount Currie Indian Band.
Behind the abandoned settlement Skatin Skookumchuck, where this group of In - Shuck -ch lived, the river continues its route and flows 55 km in the Harrison Lake.
The continuation of the river is called Harrison River. This river flows near Chehalis in the Fraser.
The main tributaries are the Meager Creek, the Ryan River, the Green River and the Birkenhead River.