The Walla Walla River originates in the Blue Mountains of northeastern Oregon, flowing westward through southeastern Washington before joining the Columbia River just above Wallula Gap. Its major tributary is the Touchet River, which confluences with the Walla Walla near the town of Touchet, Washington. The river system drains a watershed of approximately 1,758 square miles across the two states.

Paddling opportunities on the Walla Walla are primarily concentrated on its lower reaches as it approaches the Columbia. This section offers a flatwater to Class I experience, characterized by deep oxbows with steep, brushy banks. The meandering nature of the river creates a leisurely paddling environment ideal for kayaking and fishing, particularly for smallmouth bass. The river's difficulty is generally suitable for beginners, though wind conditions can occasionally present challenges.

Late spring through early fall provides the best paddling conditions, with autumn offering particularly scenic views as foliage colors peak along the riverbanks. Flora along the lower Walla Walla includes big sage on the hillsides and a variety of riparian vegetation lining the banks. Wildlife enthusiasts may spot numerous bird species, and the river supports populations of steelhead and bull trout.

Key landmarks include the confluence with the Touchet River and the river's mouth at the Columbia. The town of Walla Walla serves as a primary access point, with additional put-ins available near Milton-Freewater, Oregon and at various points as the river approaches the Columbia.

Historically, the Walla Walla River valley was home to the Walla Walla and Cayuse tribes. The river played a crucial role in early settlement and agricultural development of the region, particularly for its importance in irrigation.

Safety considerations include checking water levels and wind conditions before embarking. Regulations are minimal for private paddlers, but commercial outfitters require permits. While multi-day trips are less common on the Walla Walla itself, paddlers seeking longer adventures often combine it with sections of the nearby Snake or Columbia Rivers. The relatively calm nature of the lower Walla Walla makes it an excellent warm-up or conclusion for more extensive regional paddling itineraries.