Vegetation in the park ranges from grassland and alpine meadow to towering forests of evergreen, with the dominant sub-alpine forest spreading down the valleys. The species of vegetation in Banff National Park include an astounding 996 trees, grasses and flowers, 407 lichens, 243 mosses and 53 liverworts. The montane forest is a fairly open forest of Douglas fir, white spruce, pine, aspen and balsam. The sub-alpine forest is more dense and uniform, being almost entirely coniferous, with two kinds of spruce, fir, larch and pine. The alpine tundra area, which occurs above 2195 metres, may appear bleak, but it is a world of beautiful flowers in their dry, cold and wind-swept environment.

The park includes parts of two of the three parallel mountain systems that comprise the Rocky Mountains - the easternmost front ranges, with their slanting tabletop shape, and the casellate Main Ranges - the most complete sequence of sedimentary strata in Canada. Sculpted by glaciers a billion years ago and now separated by wide sweeping valleys and open pine forest, their angular peaks rise as high as 4000 metres of staggering natural beauty. Although the icefields and glaciers do not teem with life, as the forest and alpine zones do, they are the park's main source of water draining into beautiful alpine lakes, or tarns, some of which like Lake Louise are world famous. The picture-perfect Lake Louise sits beneath a vast bowl of mountains and glaciers, its eastern shore site of a giant glacial moraine. The peacock blue of the Rockies' lakes is caused by the particles of glacial silt, which absorbs all but the blue-green range of colours from incoming light.