Ilex anomala is a dioecious tree or occasionally shrub, ranging from 1 to 12 meters in height. The leaves are simple and alternate, with blades that are oblanceolate, elliptic to ovate, obovate, or sometimes suborbicular, measuring between 3 to 19 cm in length and 1.5 to 9.5 cm in width. The apex of the leaves is typically rounded to obtuse and rarely emarginate, with the base tapering to the petioles. The leaves are glabrous, with a dark green and glossy upper surface and a paler lower surface. They are thick and coriaceous, with mature leaves having subentire margins, although seedling leaves may be serrated. The veins are conspicuously reticulate, impressed on the upper surface, and appear watery on the lower surface in fresh material. The petioles range from 0.5 to 3.5 cm long and have very small stipules. The flowers are unisexual, occasionally producing some flowers that appear bisexual (perfect). They are organized in cymose panicles that are 2 to 10 cm long, with flattened peduncles that are 1.3 to 5 cm long. The pedicels are about 2 to 6 mm long with two bracteoles below the middle, each 2 to 3 mm long. The calyx has four very broadly ovate lobes, each 1.5 to 2 mm long and 2 to 3 mm wide, with hyaline and often erose margins. The corolla lobes are 6 to 10 in number, oblong-elliptic, and range from 3 to 4.5 mm in length. The stamens in pistillate (female) flowers have abortive anthers or are sometimes absent altogether. The ovary is superior and has 10 to 24 cells, with a sessile stigma, and features 12 to 24 lines; it is rudimentary in staminate (male) flowers. The fruit is drupaceous and contains as many 1-seeded pyrenes as carpels. It is purplish-black and globose and measures approximately 5 to 7 mm in height and 7 to 10 mm in diameter. The seeds contain an abundant supply of oily or proteinaceous endosperm. It is found in mesic to wet forests and sometimes in open bogs, at elevations ranging from 50-1,950 meters, although most commonly found between 600-1,400 meters.