Tumtum Mountain is located among the foothills of the Cascade Range, about 2 miles (3 km) east of Washington State Route 503 via NE Healy Rd, whose junction is just north of the Mount St. Helens National Volcanic Monument headquarters in Chelatchie (officially Amboy, Washington). Healy Rd becomes Forest Road 54 as it enters Gifford Pinchot National Forest and traverses along the northern base of Tumtum Mountain, and a gated logging road ascending the north flank provides access to the mountain.