The High Cascades portion is characterized by steep to moderate slopes and includes many basin areas with lakes, meadows, and rock outcrops. The Western Cascades portion is typified by steep, dissected slopes.

There is an impressive array of lakes scattered throughout the Wilderness which includes the Six Lakes Basin, Eddeeleo Lakes, and Quinn Lakes. Located just outside the eastern boundary of the wilderness is Waldo Lake, one of the purest in the world. This lake, scooped out by ancient glaciers, covers 10 square miles and reaches a maximum depth of 420 feet. On a clear day, you can see to depths of 100 feet.

Waldo Lake Wilderness area covers 36,572 total acres. There are approximately 84 miles of trails which lead to many lakes and small meadows. Waldo Lake Trail (not in wilderness) provides users with a 22-mile loop around Waldo Lake. The High Cascades are mostly Douglas-fir, mountain hemlock, and Pacific silver fir. This Wilderness is approximately 98% forested.