A northern extension of the flat interior plains that dominate the Prairie provinces, the Taiga Plains feature typically subdued relief consisting of broad lowlands and plateaus. The nearly level to gently rolling plains are occasionally interrupted by some of the larger river valleys, which can be hundreds of metres deep.

Underlying these landforms are horizontal beds of sedimentary rock consisting of various combinations and ages of limestone, shale, sandstone, and conglomerates. Many of the limestone deposits contain clearly visible fossils of marine creatures that lived here hundreds of millions of years ago. Trapped in isolated pockets and cracks within the sedimentary layers are rich natural reservoirs of oil and gas, created from the carbon residues of early life forms.

Several waves of glaciers over the region have left behind deposits of sand, gravel, and boulders. These glacial moraine areas predominate and occur in various forms and thicknesses, such as the elongated ridges called drumlins and undulating and low-relief hills. Alluvial deposits are common along major rivers and the braided networks of abandoned stream beds. Large wetlands and muskeg dominate the lowest areas. The organic soils found in the eskers of this ecozone are generally shallow, highly acidic, and nutrient-poor. The mineral soils are also poorly developed and often frozen.

The Taiga Plains Ecozone contains most of the Northwest Territories' two "great" lakes, Great Slave and Great Bear, which were carved by glaciers along the western margin of the Canadian Shield. Numerous smaller lakes dot the broad floodplains of the ecozone, which is crisscrossed with patterns of former meandering channels and crescent-shaped oxbow lakes. Other signs of the dynamic power of large rivers include steep, fast-eroding riverbanks and ice-scoured shores.

The ecozone experiences considerable variation in daylight over the course of a year. Areas north of the Arctic Circle endure at least one day in which the sun never rises and at least one in which it never sets.

The subarctic climate is characterized by short, cool summers and long, cold winters. Precipitation is low to moderate, averaging 250 to 500 mm a year across much of the ecozone. Snow and freshwater ice-cover persist for six to eight months annually.