Eucalyptus codonocarpa is a slender mallee that typically grows to a height of and forms a
lignotuber. The bark is smooth, grey, yellow or brownish and there are sometimes ribbons of shed bark hanging from the upper branches. The leaves on young plants and on
coppice regrowth are arranged in opposite pairs near the ends of the stems, linear to narrow lance-shaped, long, wide and glossy green. Adult leaves are arranged alternately, the same glossy green on both sides, lance-shaped to slightly curved, long and wide on a
petiole long. The flower buds are arranged in groups of three or seven on an unbranched
peduncle long, the individual buds on a
pedicel long. Mature buds are club-shaped, long and wide with a rounded to flattened and warty
operculum. Flowering occurs from March to June and the flowers are white. The fruit is a woody, bell-shaped
capsule long and wide, with the valves below the rim. ==Taxonomy and naming==