Cyathula uncinulata is a scrambling, straggling perennial shrub. It can grow erect and bushy in some conditions, but more often it climbs over other vegetation or sprawls along the ground. It is evergreen, keeping its leaves year-round, and grows fairly quickly, reaching lengths of anywhere from 300 mm to a substantial 6 m over time. The younger stems are noticeably hairy, with a soft, felt-like covering that ranges from whitish to yellowish. As the stems age, this hairiness thins out. One of the plant's most distinctive features is its swollen, knobby joints (nodes), where the leaves attach—a good clue for identifying it. The leaves are broad and oval to oblong in shape, typically 35 to 120 mm long and 25 to 80 mm wide. They have a short, wedge-shaped or slightly heart-shaped base and taper to a short, pointed tip. The upper surface of the leaf is moderately hairy, while the underside is much more densely covered in soft hairs, especially along the veins. Each leaf is carried on a short stalk (petiole), about 10 to 22.5 mm long.

The flowers are small and grouped into dense, rounded heads that look like little pompons. These heads are about 18 to 25 mm across when in bloom, although some may be looser and slightly oblong, enlarging to about 40 mm in diameter in fruit. They are carried on individual stalks ranging from less than 10 mm to about 40 mm long, occasionally reaching 100 mm. Each flower head is made up of compact, branching clusters, with a central fertile flower flanked by two groups of three—one fertile and two sterile, modified flowers (although this arrangement can vary). The flowers are noticeable for their straw-like bracts and bracteoles and tepals with hooked tips, which become more prominent as they mature. 

The individual flower parts, called tepals (similar to petals), are hairless, sharply pointed, and narrow. The two outer tepals are longer, about 5 to 6.5 mm, with a single vein that often ends in a tiny, fish-hook-like tip. The inner tepals are shorter, 2.5 to 5 mm, with two or three veins, and end in a small, abrupt point. The sterile, modified flowers have two bracteole-like structures with hooked tips, and two shorter hooked spines—all of which give the flower head a slightly prickly feel.

The male reproductive part (filaments) are delicate and slender, about 2 to 2.5 mm long. The female reproductive part (style), is slender and about 2 mm long. The fruit is a small, ovoid capsule, roughly 2.2 mm long, with a thin, papery wall but a firm, flattish tip, containing an ovoid, brown seed about 2 mm long.