[1] From its source in the Three Sisters Range the Tanzilla River flows roughly north and northwest to the vicinity of the community of Dease Lake, then turns west and southwest, flowing to the Stikine River in the Grand Canyon of the Stikine.

[6][7] The Tanzilla River originates in the Three Sisters Range, whence it flows northwest toward the community of Dease Lake.

Near Dease Lake the river flows by Tanzilla Butte and Tatsho Mountain.

[14][15] After Dease Lake the Tanzilla River flows through wetlands in a meandering path, north of the Hotailuh Range.

[16] Telegraph Creek Road, which connects the community of Telegraph Creek to the Stewart-Cassiar Highway, follows the Tanzilla River from Dease Lake to the Stikine River.