It is a bushy, many-branched shrub, very similar to Darwinia diosmoides but differs in the arrangement of its flowers, its more branched habit, prominent oil glands on the younger stems and its thinner, paper-like bracteoles.

Darwinia capitellata is a many-branched shrub growing to 1.0 metre (3 ft) high with its leaves crowded near the ends of the branches.

[2] The first formal of Darwinia capitellata was published in 1983 in Nuytsia by Barbara Rye, the first publication of a new species by the prolific taxonomist.

[4] It was first recognised as a distinct species when some specimens were found to have 12 chromosomes, rather than the usual 7 or 14 for Darwinia diosmoides, evidence that was later confirmed by comparison of their morphology.

[3] The specific epithet (capitellata) is from the Latin word capitatus with the diminutive -ell-, hence meaning "forming a small head",[5] referring to the arrangement of the flowers in this species.