The river is formed by the confluence of the Brerachan Water and the Allt Fearnach at Straloch, 3 miles from the top of the valley. It flows past Kindrogan House and Enochdhu, where it takes in the Dirnanean Burn, and then through Kirkmichael. It flows on past Ballintuim and Bridge of Cally, half a mile south of which it joins the Black Water to form the River Ericht. The Ericht is a tributary of the River Isla, which in turn flows into the River Tay.
The Ardle is bridged at Enochdhu, Kirkmichael, Pitcarmick, Dalnabreck, Ballintuim, Blackcraig, Cally Lodge and by the A93 at Bridge of Cally.
The name Ardle according to legend is from a Pictish warrior who was killed in battle at Enochdhu. He was reputed to be a giant, and the mound of his supposed grave is located in the garden of Dirnanean Lodge in Enochdhu.
The 'giant's grave' is 19 feet long, and around 3 feet wide. At its end is a monolith 5 feet high. The origin of this stone is unknown but it is thought unlikely to be prehistoric.