MT 38 begins south of Hamilton, at an intersection with U.S. Highway 93 (US 93). Initially, the highway heads south along a former section of US 93. The road takes an abrupt turn eastward as it passes through Grantsdale, begins its meandering climb southeast along Skalkaho Creek and northeast along Daly Creek through the Sapphire Mountains, turning southeast again before it crosses Skalkaho Pass. From the pass, MT 38 descends along the West Fork Rock Creek, past the Gem Mountain sapphire mine and crosses Rock Creek near its headwaters, going into Eagle Canyon before making a northeasterly run to its terminus at MT 1, south of Phillipsburg and west of Anaconda.