The leaves of american holly are thick, leathery, and deep green, measuring 2-4 inches (5-10 cm) in length. They are oblong to elliptic in shape with spiny marginal teeth. The leaves are alternate, simple, and coriaceous, featuring an apical spine, which is a distinctive identifying characteristic. Their texture is firm, contributing to the overall robustness of the plant. The marginal spines and overall form make these leaves easily recognizable for botanical enthusiasts.

American holly exhibits greenish-white flowers that typically bloom between April and June. Male flowers appear in clusters of 3-12, while female flowers are found solitarily or in pairs or threes. The male inflorescence is a cyme, and the female flowers are single. Each flower is typically small, around 0.25-0.33 inches (6-8 mm) across, with petals arranged symmetrically. The flowers emit a mild, pleasant aroma, making them easily identifiable to plant enthusiasts.

The stem of american holly is primarily greenish-gray in color, with a smooth texture when young and becoming rougher with age. Stems are moderately thick, typically ranging from 0.5 to 1.5 inches (1.3 to 3.8 cm) in diameter. They exhibit a branching pattern that is somewhat irregular, with branches emerging randomly along the stem. One distinctive feature is the presence of small, slightly raised lenticels scattered across the surface, aiding in gas exchange.

The fruit of american holly are distinctive, berry-like drupes that exhibit a vibrant red to orange hue. These spherical fruits typically measure about 0.25 to 0.5 inches (6 to 13 mm) in diameter. They showcase a smooth texture and robust nature, notably persisting on the tree from early fall through the winter months of September to February. To successfully produce these fruits, both male and female plants must be in proximity for effective pollination, as the species is dioecious. Once pollinated, the female plants bear the colorful fruits which are a prominent feature for species identification.