Isodendrion pyrifolium is a species of branched shrubs typically reaching heights of about 80 to 200 cm. These shrubs are characterized by their pilose branches, particularly when young, with antrorsely appressed hairs, and the branches tend to become more glabrate as they age. The leaves are simple and alternate, with elliptic-ovate to elliptic-oblanceolate or occasionally lanceolate blades measuring 2.5 to 6.5 cm in length and 0.8 to 3.2 cm in width. The apex of the leaves is obtuse and often features a small, sharp extension known as a mucro. The leaf base is rounded to broadly cuneate. The leaf surfaces range from sparsely to moderately pilose, particularly along the veins, and the blades are chartaceous. The margins are serrulate to nearly entire and feature a whitish ciliate edge. The veins are conspicuously reticulate, slightly raised on the upper surface, and more pronounced on the lower surface. Petioles are between 0.5 and 1 cm short and exhibit appressed pilose hairs. The stipules are slightly asymmetrical, deltate-ovate, and measure 2.8 to 5 mm long. These stipules have a raised, thickened midrib that is appressed whitish puberulent and becomes brownish, dry, and membranous toward the margins. The flowers are solitary and axillary, supported by peduncles 2 to 6 mm long with a whitish puberulent texture. The flowers are fragrant and perfect (bisexual), situated on short pedicels measuring 1.5 to 4 mm long and whitish-puberulent. The calyx consists of five lanceolate sepals, 3.5 to 5 mm long, which become membranous towards the whitish ciliolate margins. The corolla likely exhibits a greenish-yellow hue, with the upper petals measuring 10.5 to 12.3 mm long and the lobes ranging from 3.5 to 5 mm long. The lateral and lower petals are slightly larger. The stamens are subequal; the ovary is superior, 3-carpellate, and 1-celled with parietal placentation. The fruit is an ovoid-ellipsoid capsule approximately 12 mm long and 3-valved. The seeds are olive-colored with a dark spot near the middle, measuring about 3 to 3.2 mm in length and 1.8 to 2.2 mm in diameter, containing fleshy, oily endosperm. It is typically found in low-elevation dry sites between 363-964 meters.