Deua River rises about 5 kilometres (3.1 mi) southeast of Bendethera Mountain, on the eastern slopes of the Badja Range, part of the Great Dividing Range, within Deua National Park in rugged and thickly forested ranges south of Braidwood. The river flows generally south, west, north, northeast, south southeast and east, making almost a complete circuit, joined by fourteen minor tributaries before reaching its confluence with the Moruya River near Kiora. The river descends 634 metres (2,080 ft) over its 139 kilometres (86 mi) course.
The lower reaches of the river are estuarine by nature and are called the Moruya River. This upper catchment is located in a rain shadow, so the Deua River is on the whole a small river, and naturally experiences periods of very low flow.
The village of Araluen lies in the valley of Araluen Creek, that joins the Deua River at roughly the midpoint in its course. The name 'Araluen' means 'water lily' or 'place of the water lilies' in the local aboriginal dialect. At the time of European settlement Araluen was described as a broad alluvial valley with many natural billabongs covered with water lilies. Unfortunately, no such billabongs exist in the Araluen valley today. As with most river and creek valleys in south-eastern Australia, the natural landscape of Araluen Creek and its valley were completely destroyed by rampant and extremely destructive gold mining in the latter half of the 19th century. This has mobilised thousands of tons of coarse granitic sands and lead to serious sand-slugging or sand siltation of the lower half of the Deua River below the Araluen Creek confluence. Nevertheless the Deua River supports valuable populations of the threatened Australian grayling and several other native freshwater fish species.