In British Columbia, the highway is entirely in mountainous regions and is also known as the Southern Trans-Provincial Highway. At Hope, Highway 3 connects to the #1 Trans-Canada heading north up the Fraser Valley (north to Lytton and Cache Creek, and west to Chilliwack, Abbotsford, and Vancouver).
Just 7 km east of Hope is the junction with the #5 Coquihalla Highway (north to Merritt and Kamloops). The first segment between the Coquihalla Highway at Hope to Highway 5A (the Hope-Princeton Highway) passes by the site overlooking the Hope Slide and then winds through the scenic Manning Provincial Park, up and over Allison Pass (elevation 1,342 m, 4403 ft).
The only non-mountainous portion is the stretch east of Princeton to Osoyoos through there wide Similkameen River Valley, which still has mountains, but it doesn’t feel mountainous. In the Similkameen, you pass many lush farms and the town of Keremeos before dropping down to Osoyoos in the Okanagan Valley (route 3 A detours north to Penticton).
At Osoyoos you can head north on Highway 97 to Penticton, Kelowna and Vernon before proceeding to a choice of Kamloops, Salmon Arm and Sicamous (via 97, 97A, or 97B respectively) on the main Trans-Canada.
From Osoyoos the eastbound leg is entirely mountainous until east of Alberta’s Crowsnest Valley. The highway climbs sharply east of Osoyoos and then follows the Kettle Valley eastward (it flows into the mighty Columbia River) past the communities of Rock Creek, Midway (where the Kettle river veers through the US), Grand Forks (where the Kettle River returns into Canada), and Christina Lake (where the Kettle River decisively heads southwards).
From Christina Lake, the highway climbs northward to Bonanza Pass (1,535 m or 5,036 ft) at Nancy Green Lake (you can take highway 3B south to Rossland and Trail) before heading east to Castlegar at the south end of Upper Arrow Lake on the Columbia River. On the west side of Arrow Lake are the scenic towns of Nelson and Kaslo.
From Castlegar, the highway heads eastward along the Pend d’Oreille River to Salmo up and over the Kootenay Pass (elevation 1,775 m or 5,823 ft; watch for wintertime avalanche closures here) to Creston, which lies at the southern end of Kootenay Lake in a wide lush agricultural paradise. From Creston you can take Route 3A north on the east side of Kootenay Lake to the ferry at Kootenay Bay to Proctor, connecting back to Nelson and Castlegar.
About 70 kilometres east of Creston, just south of Yahk, highway 3 comingles with the north-south Highway 95 up to Cranbrook, with the ski town of Kimberley close-by. From Cranbrook, you can head north on Highway 95 to Radium and Golden, or north on 93 to Radium, Lake Louise and Jasper. East of Cranbrook, Highway 3 comingles with Highway 93 to Elko, and then heads east to the ski town of Fernie. After Fernie, the Crowsnest highway continues eastward through Sparwood and the Alberta border a the Crowsnest Pass.