It flows generally north about 150 km (93 mi)[4] to join the Nahlin River.

[10] The mouth of the Sheslay River is located about 145 km (90 mi) northeast of Juneau, Alaska and about 110 km (68 mi) northwest of Telegraph Creek, British Columbia.

The Sheslay River's watershed covers 3,342 km2 (1,290 sq mi),[5] and its mean annual discharge is 65.3 m3/s (2,310 cu ft/s).

The lower Sheslay River, below the mouth of the Samotua River, flows just south and west of Heart Peaks, part of the Nahlin Plateau.

The lowermost Sheslay River flows between the Taku and Nahlin Plateaus.