Barrel Cactus features long, recurved spines that are modified leaves. These spines are densely packed and can grow up to 6 inches (15 cm) in length. They exhibit a variety of colors including whitish, yellow, and reddish hues. The texture of these spines is rigid and pointed, deterring herbivores. Each spine is single-veined, and their arrangement provides a distinctive, star-like appearance around the plant's central stem, aiding in water conservation and temperature regulation.

The flowers of barrel Cactus are a striking spectacle, emerging from the top of the plant in a distinctive ring pattern. Each flower is funnel-shaped and boasts an array of numerous petals. These petals exhibit bright colors, often ranging from yellow to vivid shades of pink and red. The flowers typically measure about 2–3 inches (5–7.5 cm) in diameter. Blooming predominantly occurs in late spring through summer, adding vibrant hues and a touch of elegance to their arid habitats.

The stem of barrel Cactus is globular to cylindrical, with a thick and ribbed structure. It typically measures up to 3 feet (90 cm) in height and 1.5 feet (45 cm) in diameter. The stem is covered in hard, spine-bearing tubercles that are densely packed, offering protection and reducing water loss. Its surface ranges from green to bluish-green in color, often featuring a wool-like fiber at the apex, particularly where the flowers emerge.

The fruit of barrel Cactus exhibits a dichotomy in its presentation, either presenting as dry with a wooly texture or as succulent spheres. When fleshy, the fruits are typically round, embodying the plant's globular motif, while the dry variants provide a contrast with their fibrous appearance. Their size can vary, but they often remain modest, not exceeding 2 inches (5 cm) in diameter. Upon maturity, these fruits may showcase a range of colors from subtle earthy hues to more pronounced tones, depending on the specific type of barrel Cactus . Such fruits are noteworthy for both their tactile and visual diversity.