Lilian Lake is connected to the bifurcating Etomami Lake via a natural swampy portage making Etomami Lake the headwaters for both the north flowing Etomami River and the south flowing Lilian River.

For most of the river's length, it is followed by the Canadian National Railway (CNR) and Highway 9.

Several small communities and parks are situated on or near the river's banks.

In 1691, Hudson's Bay Company fur trader and explorer Henry Kelsey traversed the natural portage between the Etomami and Lilian Rivers while in search of a route to the aspen parkland region.

Fish commonly found in Lilian River include northern pike.