Marlborough

The highway leaves State Highway 1 at Blenheim, initially travelling west through Woodboune to Renwick. At Renwick the highway turns north, crossing the Wairau River and following the Kaituna River valley to meet Pelorus Sound/Te Hoiere at Havelock. From Havelock, the highway heads inland up the valley of the Pelorus River. At Pelorus Bridge the highway again turns north through Rai Valley, and crosses into Nelson region at the Rai Saddle.

Nelson-Tasman

The highway then tends southwest as it crosses over the Whangamoa Saddle approaching the coast of Tasman Bay / Te Tai-o-Aorere. The highway travels through the city of Nelson and nearby town of Richmond, continuing southwest across the plains of the Wairoa and Motueka Rivers.

From these plains, the road ascends rapidly to the 634-metre Hope Saddle. From here, the highway heads generally westward, along the valley of the Buller River and its tributaries. Beyond Murchison, this valley narrows to become the scenic Buller Gorge, and the highway twists its way high above the waters of the river.

West Coast

The highway leaves the river as its valley broadens, turning south six kilometres from Westport, where the river reaches the sea. From here, the highway keeps close to the Tasman coast from Charleston for over 100 kilometres, turning inland only briefly near Runanga. This 100-kilometre stretch includes two of the coast's larger towns, Greymouth and Hokitika.

From Hokitika, the highway moves away from the coast, though still generally keeps within five kilometres of the sea. The highway continues south past Ross and Harihari, moving through state forests as it crosses several fast-moving rivers. Seventy kilometres south of Harihari, the highway skirts Lake Mapourika and reaches the tourist settlement of Franz Josef Glacier. The glacier itself, one of two within easy walking distance of the highway, lies nearby in the Southern Alps, which here come very close to the Tasman coast. The second glacier, Fox Glacier is located some 20 kilometres further south. The highway again briefly touches the coast at Bruce Bay before heading inland past Lake Paringa, before reemerging on the Tasman coast at Knights Point. The 30 km stretch of highway from here south to Haast is noted for its rugged scenery. After crossing the Haast River, the highway turns eastward and inland up the river's valley, climbing past the Gates of Haast and crossing the 563-metre Haast Pass, the southernmost of the three main road passes across the Southern Alps.

Otago

From here, the highway again turns south, following the Makarora River valley to the northern tip of Lake Wānaka. The highway skirts the eastern coast of the lake before crossing The Neck, a saddle in the mountains that lie between Lakes Wānaka and Hāwea. The highway continues along the western shore of Hāwea, then south along the Cardrona River to Albert Town, close to the tourist centre of Wānaka.

Ten kilometres from Wānaka, the highway is met by SH 8A, a spur of SH 8 skirting the shore of Lake Dunstan. SH 6 continues south along the western shore of the Lake, paralleling SH 8 which lies on the eastern shore. Close to Cromwell, a second spur, SH 8B, connects the two highways. From here, SH6 turns west, following the narrow and twisting Kawarau Gorge, emerging close to the wine-producing area of Gibbston.

At the western end of the Kawarau Gorge, midway between Cromwell and Queenstown, the highway passes the Nevis Bluff, a steep schist rock outcrop rising 100 m above the Kawarau River. The highway has a history of being disrupted and closed at this point due to instability and rock falls from the bluff. The first road around the bluff was constructed in 1866, opening access to the Wakatipu goldfields.^[2] Significant slips occurred at the bluff on 1940-02-20,^[3] and blocking SH6 in June 1975.^[4] On 17 September 2000, a large-scale rock fall buried the highway at the bluff, and several motorists narrowly avoided being killed. The fall was caught on video and showed a volume of 10,000 m³ for the main fall; the resulting dust cloud was seen 5 km away.^[5][6] Transit New Zealand conducted stabilisation drilling and blasting at the bluff twice in 2006 and again in 2007.^[7]

From the Nevis Bluff, the highway continues west, reaching Frankton, close to the shore of Lake Wakatipu. The highway turns south to follow the southeastern shore of the lake, skirting the foot of The Remarkables and the Hector Mountains. This stretch of the highway is in part tortuously winding, and rises and falls over a stretch known as "The Devil's Staircase".

Southland

The highway leaves the lake's shore at Kingston, continuing south to Garston, where, the highway briefly follows the course of the infant Mataura River before heading across the Jollies Hill Pass to the upper reaches of the Ōreti River near Lowther. The highway continues to follow the Ōreti south, through Lumsden, then across the Southland Plains, past the town of Winton before reaching its terminus at a junction with SH 1 in central Invercargill.