[4] Draining a basin of 2,450 square miles (6,300 km2), it enters the Columbia near the city of Umatilla in the northeastern part of the state.

Coombs Creek enters from the left about 3 miles (4.8 km) below that, and then the river, turning north, flows along Fort Henrietta Park in the city of Echo and under I-84 again.

The Umatilla reaches Stanfield about 23 miles (37 km) from the mouth, then passes under Oregon Route 207 and receives Butter Creek from the left.

Public access to salmon and steelhead fishing is fairly good downstream of the Oregon Route 11 bridge.

Upstream of the bridge, the river runs through the Umatilla Indian Reservation, where fishing is limited to those with a tribal permit.