From the townland of Graigaman, in the civil parish of Buolick in the barony of Slievardagh, the King's River drains the southern side of the Slieveardagh Hills.

Flowing southeast, it crosses into County Kilkenny where it is joined by the Munster River.

The King's River begins[4] with the Coalbrook[5] and Garranacoll[6] streams.

[15] The King's River is then joined by the Ennisnag stream[16] before flowing into the Nore.

[17][18] Additional tributaries include one that starts as a spring in the townland of Ballyphilip, Balingarry Civil Parish, joining the river above Wilford, one above Enterprise Centre, near Ballingarry, and one at Rivergrove, Kilkenny.