Tenmile Creek rises near the top of the Continental Divide on the east slopes of the Rocky Mountains, specifically the Lewis and Clark Range. The upper watershed consists of steep, forested mountain slopes. The lower watershed consists of the final of the stream, which travels over prairie and through residential and retail developments in and near the city of Helena, Montana before reaching its outlet at Prickly Pear Creek. Lake Helena is only downstream from the confluence of Tenmile Creek and Prickly Pear Creek.